Luke 18:19

The Saviour then considering his meaning, because faith is the way to good works, passes over the question he asked, and leads him to the knowledge of faith; as if a man was to ask a physician, "What shall I eat?" and he was to show him what ought to go before his food. And then He sends him to His Father, saying, Why callest thou me good? not that He was not good, for He was the good branch from the good tree, or the good Son of the good Father.

He does not deny that He is good, but points to God. None is good then except he be full of goodness. But should it strike any one that it is said, none is good, let this also strike him, save God, and if the Son is not excepted from God, surely neither is Christ excepted from good. For how is He not good who is born from good? A good tree brings forth good fruits. (Matt. 7:17.) How is He not good, seeing that the substance of His goodness which He took unto Him from the Father has not degenerated in the Son which did not degenerate in the Spirit. Thy good spirit, he says, shall lead me into a land of uprightness. (Ps. 148:10.) But if the Spirit is good who received from the Son, verily He also is good who gave It. Because then it was a lawyer who tempted Him, as is plainly shown in another book, He therefore well said, None is good, save God, that He might remind him that it was written, Thou shalt not tempt the Lord thy God, (Deut. 6:16.) but he the rather gives thanks to the Lord that He is good. (Ps. 118.)

(Quæst. Ev. lib. ii. qu. 63.) It may seem that the account given in Matthew is different, where it is said, "Why askest thou me of good?" which might apply better to the question which he asked, What good shall I do? (Matt. 10.) In this place he both calls Him good, and asks the question about good. It will be best then to understand both to have been said, Why callest thou me good? and, Why askest thou me of good? though the latter may rather be implied in the former.

Now he thought to detect Christ in blaming the law of Moses, while He introduced His own commands. He went then to the Master, and calling Him good, says that he wishes to be taught by Him, for he sought to tempt Him. But He who takes the wise in their craftiness answers him fitly as follows, Why callest thou me good? there is none good, save God alone. But the ruler expected to hear Christ say, Forsake the commandments of Moses, and listen to Mine. Whereas He sends him to the former; as it follows, Thou shalt not kill, Thou shalt not commit adultery. The ruler was not able to contain the new word, but being like an old bottle, burst with sorrow.