(3) باب فِي الأَمْرِ بِالتَّيْسِيرِ وَتَرْكِ التَّنْفِيرِ
It has been narrated on the authority of Abu Masa that when the Messenger of Allah (ﷺ) deputed any of his Companions on a mission, he would say:
Give tidings (to the people) ; do not create (in their minds) aversion (towards religion) ; show them leniency and do not be hard upon them.
Reference: Sahih Muslim 1732
In-book reference: Book 32, Hadith 6
USC-MSA web (English) reference(deprecated numbering scheme): Book 19, Hadith 4297