Sahih Muslim | Book 19 | Chapter 3

Narrated by
It has been narrated on the authority of Abu Masa that when the Messenger of Allah (may peace be upon him) 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.

Narrated by Sa'd b. Abu Burda
It has also been narrated by Sa'd b. Abu Burda through his father through his grandfather that the Prophet of Allah (may peace be upon him) 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.

Narrated by
This hadith has been transmitted on the authority of Buraida but for the last two words.

Narrated by The Messenger of Allah (may peace he upon him) has been
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.