Albert Barnes on Matthew 19:16

One came. This was a young man, Mt 19:20. He was a ruler, (Luke;) probably a ruler in a synagogue, or of the great council of the nation; a place to which he was chosen on account of his unblemished character, and promising talents. He came running, (Mark;) evincing great earnestness and anxiety. He fell upon his knees, (Mark;) not to worship him, but to pay the customary respectful salutation; exhibiting the highest regard for Jesus as an extraordinary religious Teacher.

Good Master. The word good here means, doubtless, most excellent; referring not so much to the MORAL character of Jesus as to his character as a religious Teacher. It was probably a title which the Jews were in the habit of applying to their religious teachers. The word Master here means Teacher.

What good thing shall I do. He had attempted to keep all the commandments. He had been taught by his Jewish teachers that men were to be saved by doing something, or by their works; and he supposed that this was to be the way under every system of religion. He had lived externally a blameless life; but yet he was not at peace: he was anxious, and he came to ascertain what, in the view of Jesus, was to be done, that his righteousness might be complete. To have eternal life means, to be saved. The happiness of heaven is called life, in opposition to the pains of hell, called death, or an eternal dying, Rev 2:2, 20:14. The one is real life, answering the purposes of living--living to the honour of God, and in eternal happiness; the other is a failure of the great ends of existence--prolonged, eternal suffering--of which temporal death is but the feeble image.

(l) "what good" Mk 10:17, Lk 10:25, 18:18