The Book of Jihad and Expedition (Kitab Al-Jihad wa'l-Siyar)
Muslim :: Book 19 : Hadith 4297
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.
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