Allah Subhanuhu wa-T'ala says in the Holy Quran:
إِنَّ الَّذِينَ آمَنُواْ وَعَمِلُواْ الصَّالِحَاتِ يَهْدِيهِمْ رَبُّهُمْ بِإِيمَانِهِمْ تَجْرِي مِن تَحْتِهِمُ الأَنْهَارُ فِي جَنَّاتِ النَّعِيمِ
دَعْوَاهُمْ فِيهَا سُبْحَانَكَ اللَّهُمَّ وَتَحِيَّتُهُمْ فِيهَا سَلاَمٌ وَآخِرُ دَعْوَاهُمْ أَنِ الْحَمْدُ لِلّهِ رَبِّ الْعَالَمِينَ
Surely those who believe (in the truths revealed in the Book) and do righteous deeds their Lord will guide them aright because of their faith. Rivers shall flow beneath them in the Gardens of Bliss. Their cry in it will be: 'Glory be to You, Our Lord!', and their greeting: 'Peace!'; and their cry will always end with: 'All praise be to Allah, the Lord of the universe. (10:9-10)
The sequence of ideas presented here is quite significant because answers have been systematically provided to a number of highly relevant basic questions. Let us look at these answers in their sequence. Why will the righteous enter Paradise? The answer is: because they have followed the straight way in their worldly life. That is, in all matters and in every walk of life, in all affairs relating to the personal or collective life they have been righteous and have abstained from false ways.
This gives rise to another question: how were the righteous able to obtain a criterion that would enable them to distinguish, at every turn and crossroad of life, between right and wrong, between good and evil, between fair and unfair? And how did they come to have the strength to adhere to what is right and avoid what is wrong? All this, of course, came from their Lord Who bestowed upon them both the guidance which they needed to know the right way and the succour required to follow it. In answer to why their Lord bestowed upon them this guidance and succour, we are reminded that all this was in consideration for their faith.
It is also made clear that this reward is not in lieu of merely a verbal profession to faith, a profession that is no more than a formal acceptance of certain propositions. Rather, the reward is in consideration for a faith that became the moving spirit of a believer's character and personality, the force that led him lo righteous deeds and conduct. We can observe in our own physical lives that a person's survival, state of health, level of energy, and joy of living all depend upon sustenance from the right kind of food. This food, once digested, provides blood to the veins and arteries, provides energy to the whole body and enables the different limbs to function properly.
The same holds true of man's success in the moral domain. It is sound beliefs which ensure that he will have the correct outlook, sound orientation and right behaviour that will ultimately lead to his success. Such results, however, do not ensue from that kind of believing which either consists of a mere profession to faith, or is confined to some obscure corner of man's head or heart. The wholesome results mentioned above can only be produced by a faith which deeply permeates man's entire being, shaping his mental outlook, even becoming his instinct; a faith which is fully reflected in his character, conduct and outlook on life. We have just noted the importance of food. We know that the person who, in spite of eating remains like one who has not partaken of any food, would not be able to enjoy the healthy results that are the lot of the person who has fully assimilated what he ate. How can it be conceived that it would be different in the moral domain of human life? How can it be that he who remains, even after believing, like the one who does not believe, will derive the benefit and receive the reward meant for those whose believing leads to righteous living?
"...their cry will always end with: 'All praise be to Allah, the Lord of the universe."
This should remove any misconceptions about Paradise which seem to have been formed by some people of frail understanding. Subtly, the verse suggests that when people are admitted to Paradise, they will not instantly pounce upon the objects of their desire as the starved and hungry are wont to do when they observe food. Nor will they frantically go about giving vent to their lusts, impatiently demanding their cherished objects of enjoyment - beautiful women, wine, dissolute singing and music.
The fact is that the men of faith and righteousness who are admitted to Paradise will be those who, during their life in the world, have embellished their lives with sublime ideas and noble deeds, who have refined their emotions, who have oriented their desires in the right direction, and who have purified their conduct and character. Thus, the nobility which they have developed in their personalities will shine in even greater splendour when they set their feet in the pure and clean environment of Paradise. Those same traits which characterized their behaviour in the world will appear with even greater lustre.
The favourite occupation of such people in Paradise will be the same as during their life on the earth - to celebrate the praise of God. Likewise, their relationships in Paradise will be imbued with feelings of mutual harmony and concern for each other's well-being as had been the case in this world.
"By the grace of Allah, you are gentle towards the people; if you had been stern and harsh-hearted, they would have dispersed from round about you." The noble Qur'an, A'al-Umran(3):159
The following is a Hadith from the books of Bukhari and Muslim:
Hadrat Anas ibn Malik (may Allah be pleased with him) said: While we were in the mosque with Allah's Messenger (may Allah's blessings and peace be upon him) a desert Arab came and began to pass water in the mosque. The companions of Allah's Messenger said, "Stop! Stop!" but Allah's Messenger (may Allah's blessings and peace be upon him) said, "Don't interrupt him; leave him alone." They left him alone, and when he had finished, Allah's Messenger (may Allah's blessings and peace be upon him) called him and said to him, "These mosques are not suitable places for urine and filth, but are only for remembrance of Allah, prayer and recitation of the Qur'an," or however Allah's Messenger expressed it.* Hadrat Ibne Malik (may Allah be pleased with him) said that he then gave orders to one of the people who brought a bucket and poured water over it. (Bukhari and Muslim)
*Indicating that the transmitter is not sure of the exact words.
According to the Holy Qur'an, there is a great difference between 'God's will' and 'God's good pleasure'. The failure to differentiate between the two often gives rise to serious misconceptions. If a certain thing takes place in accord with the universal will of God, and thus by His sanction, that does not necessarily mean that God is pleased with it.
Nothing at all takes place in the world unless God permits it to take place, unless He makes it a part of His scheme, and unless He makes it possible for that event to take place by creating its necessary conditions. The act of stealing on the part of a thief, the act of homicide on the part of a murderer, the wrong and corruption of the wrong-doer and the corrupt, the unbelief of the unbeliever and the polytheism of the polytheist - none of these are possible without the will of God. Likewise, the faith of the believer and the piety of the pious are inconceivable without the will of God. In short, both these require the will of God. But whereas the things in the first category do not please Him, those in the second do.
Even though the will of God is oriented to ultimate good, the course of the realization of that good is paved with conflict between the forces of light and darkness, of good and evil, of what is sound and pure on the one hand and what is corrupt and defiled on the other. With larger interests in view, God has endowed man with the disposition of obedience as well as of disobedience. He has created in man Abrahamic and Mosaic as well as Nimrodic and Pharaonic potentialities. Both the pure, unadulterated human nature and the satanic urges are ingrained in man's being and have been provided with the opportunity to work themselves out by coming into conflict with each other. He has granted those species of His creatures who are possessed of authority (viz. man and jinn) the freedom to choose between good and evil. Whosoever chooses to act righteously has been given the power to do so, and the same is the case with him who chooses to be evil. People of both categories are in a position to use material resources within the framework of the broader considerations underlying God's governance of His universe. God will be pleased, however, only with those who are working for good. God likes His creatures to exercise their freedom of choice properly and commit themselves to good of their own volition.
Unlike the angels, who carry out God's commands without resistance from any quarter, the task entrusted to men is to strive to establish the way of life sanctioned by God in the face of opposition and hostility from evil-doers and rebels against Him. In the framework of His universal will, God allows even those who have chosen the path of rebellion to strive for the realization of their goals, even as He grants the believers every opportunity to strive along the path of obedience and service to God. Despite this granting of freedom and choice to all there is no doubt that God is pleased with, and guides, directs, supports and strengthens the believers alone because their overall direction is to His liking. Nevertheless, they should not expect that by His supernatural intervention God will either force those who are disinclined to believe into believing or that He will forcibly remove the satanic forces - among both men and jinn - who are resolved to spare neither their mental and physical energy nor their material resources to impede the triumph of the Truth. Those determined to strive in the cause of the Truth, and of virtue and righteousness are told that they must prove their earnest devotion by waging a fierce struggle against the devotees of falsehood. For had God wanted to use miracles to obliterate falsehood and usher in the reign of the Truth, He would not have required human beings to accomplish the task. He could have simply seen to it that no evil one remained in the world, leaving no possibility for polytheism and unbelief to exist. (Tafheemul Quran)