He who disapproves is guiltless, and he who disapproves is safe. Qatadah said : it means one who feels its disapproval in his heart, and one who expresses disapproval in his heart.
عَنِ النَّبِيِّ ﷺ بِمَعْنَاهُ قَالَ فَمَنْ كَرِهَ فَقَدْ بَرِئَ وَمَنْ أَنْكَرَ فَقَدْ سَلِمَ قَالَ قَتَادَةُ يَعْنِي مَنْ أَنْكَرَ بِقَلْبِهِ وَمَنْ كَرِهَ بِقَلْبِهِ
Amirs will be appointed over you, and you will find them doing good as well as bad deeds. One who hates their bad deeds is absolved from blame. One who disapproves of their bad deeds is (also) safe (so far as Divine wrath is concerned). But one who approves of their bad deeds and imitates them (is doomed). People asked: Messenger of Allah, shouldn't we fight against them? He replied: No, as long as they say their prayer. (" Hating and disapproving" refers to liking and disliking from the heart.)
عَنْ أُمِّ سَلَمَةَ زَوْجِ النَّبِيِّ ﷺ عَنِ النَّبِيِّ ﷺ أَنَّهُ قَالَ إِنَّهُ يُسْتَعْمَلُ عَلَيْكُمْ أُمَرَاءُ فَتَعْرِفُونَ وَتُنْكِرُونَ فَمَنْ كَرِهَ فَقَدْ بَرِئَ وَمَنْ أَنْكَرَ فَقَدْ سَلِمَ وَلَكِنْ مَنْ رَضِيَ وَتَابَعَ قَالُوا يَا رَسُولَ اللَّهِ أَلاَ نُقَاتِلُهُمْ قَالَ لاَ مَا صَلَّوْا أَىْ مَنْ كَرِهَ بِقَلْبِهِ وَأَنْكَرَ بِقَلْبِهِ
Another version of the tradition narrated on the same authority attributes the same words to the Messenger of Allah ﷺ except that it replaces kariha with ankhara and vice versa.
قَالَ رَسُولُ اللَّهِ ﷺ بِنَحْوِ ذَلِكَ غَيْرَ أَنَّهُ قَالَ فَمَنْ أَنْكَرَ فَقَدْ بَرِئَ وَمَنْ كَرِهَ فَقَدْ سَلِمَ