What is the ruling on describing a Muslim as a Jew when angry, and is that considered disbelief and nullification of good deeds?

A Muslim is not permitted to say to his Muslim brother, "O Jew," because it is an accusation of disbelief. It is mentioned in the Hadith (definition) that whoever says to his brother, "O disbeliever," then it applies to one of them. The meaning of "it returns upon him" is the return of the accusation of disbelief, not disbelief itself, as if he has disbelieved himself. The فقهاء (jurists) have stipulated that the one who says such a thing should be disciplined. The questioner must repent by feeling remorse and resolving not to repeat it, and he should supplicate for his brother in his absence. It is not necessary to inform him of the insult if he was not aware of it.