It is narrated from Imam Sadeq (AS) who said: When your believing brother’s deed looks bad to you, it is necessary that for 70 times, you (try to) find an excuse for that act. If you cannot find an excuse for him, say to yourself, maybe he has an excuse that we are not aware of it [1].
[1] Awalemul Olume wal Ma’arefe wal Ahwal,Vol. 20, page 706.
source : Shafaqna