Umm Salamah, wife of the Prophet (ﷺ) is reported to have said:

The Messenger of Allah (ﷺ) said: You will have commanders some of whom you will approve and some of whom you will disapprove. He who expresses disapproval with his tongue (Abu Dawud said : This is Hisham’s version) is guiltless; and he who feels disapproval in his heart, is safe, but he who is pleased and follows them. He was asked; shall we not kill them, Messenger of Allah? Abu Dawud’s version has : Shall we not fight with them? He replied : No, so long as they pray.

حَدَّثَنَا مُسَدَّدٌ، وَسُلَيْمَانُ بْنُ دَاوُدَ، - الْمَعْنَى - قَالاَ حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، عَنِ الْمُعَلَّى بْنِ زِيَادٍ، وَهِشَامِ بْنِ حَسَّانَ، عَنِ الْحَسَنِ، عَنْ ضَبَّةَ بْنِ مِحْصَنٍ، عَنْ أُمِّ سَلَمَةَ، زَوْجِ النَّبِيِّ صلى الله عليه وسلم قَالَتْ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏:‏ ‏"‏ سَتَكُونُ عَلَيْكُمْ أَئِمَّةٌ تَعْرِفُونَ مِنْهُمْ وَتُنْكِرُونَ فَمَنْ أَنْكَرَ ‏"‏ ‏.‏ قَالَ أَبُو دَاوُدَ قَالَ هِشَامٌ ‏:‏ ‏"‏ بِلِسَانِهِ فَقَدْ بَرِئَ، وَمَنْ كَرِهَ بِقَلْبِهِ فَقَدْ سَلِمَ وَلَكِنْ مَنْ رَضِيَ وَتَابَعَ ‏"‏ ‏.‏ فَقِيلَ ‏:‏ يَا رَسُولَ اللَّهِ أَفَلاَ نَقْتُلُهُمْ قَالَ ابْنُ دَاوُدَ ‏:‏ ‏"‏ أَفَلاَ نُقَاتِلُهُمْ ‏"‏ ‏.‏ قَالَ ‏:‏ ‏"‏ لاَ مَا صَلَّوْا ‏"‏ ‏.‏