Because however he had come to Christ as he would to a man, and to one of the Jewish doctors, Christ answered him as Man.
Wherefore it goes on: “And Jesus said unto him, Why callest thou me good? there is none good but the One God.”
In saying which He does not exclude men from goodness, but from a comparison with the goodness of God.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Hom. in Matt., 63