Sahih Muslim 132 a
It is narrated on the authority of Abu Huraira that some people from amongst the Companions of the Apostle (ﷺ) came to him and said:
Verily we perceive in our minds that which every one of us considers it too grave to express. He (the Holy Prophet) said: Do you really perceive it? They said: Yes. Upon this he remarked: That is the faith manifest.
حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا جَرِيرٌ، عَنْ سُهَيْلٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ جَاءَ نَاسٌ مِنْ أَصْحَابِ النَّبِيِّ صلى الله عليه وسلم فَسَأَلُوهُ إِنَّا نَجِدُ فِي أَنْفُسِنَا مَا يَتَعَاظَمُ أَحَدُنَا أَنْ يَتَكَلَّمَ بِهِ ‏.‏ قَالَ ‏"‏ وَقَدْ وَجَدْتُمُوهُ ‏"‏ ‏.‏ قَالُوا نَعَمْ ‏.‏ قَالَ ‏"‏ ذَاكَ صَرِيحُ الإِيمَانِ ‏"‏ ‏.‏