(When they) i.e. the lowly among the Jews; and it is also said this means the hypocrites (come unto you (Muslims), they say: We believe) in your traits and description which we find in our Scripture; (but they came in disbelief) they secretly disbelieve (and they went out in the same) disbelieving inwardly; (and Allah knoweth best what they were hiding) of disbelief.
