Allah had, as the Torah تورات itself reports, made the Jews take the pledge that they would have faith in the Holy Prophet ﷺ when he appeared. On being reminded of it, the Jews flatly denied even having taken such a pledge.
Commenting on this effrontery, the Holy Qur'an says that this is not the only instance of such a conduct on their part, for the Jews have, in fact, never fulfilled even those pledges which they acknowledge, and one group or another from among them has always been breaking the compacts they have entered into, especially with regard to religious matters. It can even be said that most of those who have been guilty of such gross violations, did not at all believe in the compacts which they made with Allah. Going against a pledge is only a sin and transgression, but having no faith in the pledge which one gives to Allah is outright infidelity.
The Holy Qur'an specifically speaks of one group or another breaking the pledge, and not of all the Jews. For there were some among them who did fulfil the pledges, so much so that many Jews finally accepted Sayyidna Muhammad as a true prophet, and joined the ranks of the Muslims.