Ahmad ibn Hanbal reported: The companions of Ibn Mas’ud, may Allah be pleased with him, if they passed by people from whom they saw something they disapproved, they would say, “Take it easy, may Allah have mercy on you.”
Source: al-Amr bil-Maʻrūf lil-Khallāl 1/25
عَنِ أَحْمَد بْن حَنْبَلٍ كَانَ أَصْحَابُ ابْنُ مَسْعُودٍ رضي الله عنه إِذَا مَرُّوا بِقَوْمٍ يَرَوْنَ مِنْهُمْ مَا يَكْرَهُونَ يَقُولُونَ مَهْلا رَحِمَكُمُ اللَّهُ
1/25 الأمر بالمعروف والنهي عن المنكر للخلال