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.
It has also been narrated by Sa'd b. Abu Burda through his father through his grandfather that the Prophet of Allah (ﷺ) sent him and Mu'adh (on a mission) to the Yemen, and said (by way of advising them)
Show leniency (to the people) ; don't be hard upon them; give them glad tidings (of Divine favours in this world and the Hereafter) ; and do not create aversion. Work in collaboration and don't be divided.
This hadith has been transmitted on the authority of Buraida but for the last two words.
The Messenger of Allah (may peace he upon him) has been reported by Anas b. Malik to have said
Show leniency; do not be hard; give solace and do not create aversion.