Sunan Ibn Majah
2203
Sahih+3

It was narrated from Jabir bin 'Abdullah that the Messenger of Allah (ﷺ) said:"May Allah have mercy on a person who is lenient when he sells, lenient when he buys, and lenient when he asks for payment

SahihAl-Albani
SahihMuhammad Fouad Abd al-Baqi