Here the "Jews" is a synecdoche for the "Jewish leaders" who opposed Jesus. Alternate translation: "The Jewish leaders said to him" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
The Jewish leaders use this question to express their shock that Jesus claims to have seen Abraham. Alternate translation: "You are less than fifty years old. You could not have seen Abraham!" (See: [[rc://en/ta/man/translate/figs-rquestion]])