Sahih Muslim
Sahih Muslim 79 b
Clarifying that faith decreases with shortcoming in obedience, and the word Kufr may be used with regard to matters other than dsbelief in Allah, such as ingratitude for blessings and not fulfilling one's duties
Arabic hadith text
وَحَدَّثَنِيهِ أَبُو الطَّاهِرِ، أَخْبَرَنَا ابْنُ وَهْبٍ، عَنْ بَكْرِ بْنِ مُضَرَ، عَنِ ابْنِ الْهَادِ، بِهَذَا الإِسْنَادِ مِثْلَهُ .
Translation
This hadith has been narrated on the authority of Abu Tahir with this chain of transmitters.