Sayyidna Jareer ibn Abdullah, Radi-Allahu anhu, once sent his servant for buying a horse. The servant made a deal for three hundred dirhams and brought the seller with him so he could be paid. Sayyidna Jareer ibn Abdullah, Radi-Allahu anhu, looked at the horse and realized that the seller had undervalued it. "Would you sell it for four hundred?" he asked. The seller agreed. "How about five hundred?" he continued his unusual "bargaining" and finally bought the horse for eight hundred dirhams. He was later asked why he did so. "The seller was not aware of the true value of this horse, " he explained. "I have simply given him a fair price because I had promised to Prophet Muhammad, Sall-Allahu alayhi wa sallam, to always be sincere and well-wisher for every Muslim."
يَا أَيُّهَا النَّبِيُّ إِنَّا أَرْسَلْنَاكَ شَاهِدًا وَمُبَشِّرًا وَنَذِيرًا وَدَاعِيًا إِلَى اللَّهِ بِإِذْنِهِ وَسِرَاجًا مُّنِيرًا" O Prophet! We have sent you as a witness, a bearer of good tidings and of warning, as a caller to Allah by His leave and as an illuminating lamp,"[Qur'an (33:45 - 46)]