Surah Al-Baqarah — Ayah 100 (2:100)
أَوَكُلَّمَا عَٰهَدُواْ عَهۡدٗا نَّبَذَهُۥ فَرِيقٞ مِّنۡهُمۚ بَلۡ أَكۡثَرُهُمۡ لَا يُؤۡمِنُونَ ١٠٠
English translation (Saheeh International)
Is it not [true] that every time they took a covenant a party of them threw it away? But, [in fact], most of them do not believe.
Brief commentary
Due to their corrupt state, a group of the Jews would always break any commitment that they made, including the duty to have faith in what the Torah revealed about the prophethood of Muhammad (peace be upon him). Most of them do not really have faith in what Allah revealed, because faith leads to keeping to and honouring commitments and promises.