I brought a bondwoman to Abu Ja'far Imam Muhammad ibn Ali Al-Baqir (as) to offer her for sale. Imam (as) began to bargain with me, and I bargained with Him (as), and then I sold her to Him (as). He (as) finalized the deal by taking possession through my hand. I said: "May I be your ransom, I was only bargaining with you (as) to see whether bargaining is permissible or not. I then said: 'I have reduced the price for you by ten dinars.'" Imam (as) said: "Far from it! Should this not have been done before finalizing the deal? Have you not heard the saying of the Messenger of Allah (swt) (peace and blessings be upon him and his family): 'Reducing the price after finalization is forbidden?'"