A short time after performing his greatest miracle, the resurrection of Lazarus, Jesus had a unique encounter with a rich young man who was a ruler (Matthew 19:20, Luke 18:18, 23). While walking with his disciples on an unknown road a man ran toward him, knelt (Mark 10:17), and asked the following.
"Good Master, what good thing shall I do, that I may have eternal life?" (Matthew 19:16, see also Mark 10:17 and Luke 18:18, HBFV throughout).
Jesus doesn't immediately answer the man's question but addresses his salutation of "good master."
"Why do you call Me good? No one (Strong's #G3762 meaning, "not even one man or woman") is good except one; that is God . . ." (Mark 10:18).
It certainly seems Jesus is admitting that he was not good. What could his answer possibly mean or teach?
A Righteous Life
The Bible teaches that Jesus was a member of the Godhead who became human (John 1:1 - 3, 14). Although he had human nature, he also possessed the Holy Spirit without measure (John 3:34). The spirit made it possible for him not to sin, in either thought or deed, during his earthly existence (2Corinthians 5:21, Hebrews 4:15, 1Peter 2:22).
Jesus' life was filled with so many merciful acts and miracles that the Apostle John admitted it would be impossible to write them all down (John 21:25). Even God the Father himself conveyed, on two separate occasions, his glowing approval of how his Son was living his life (Matthew 3:17, 17:5). The Lord clearly led a holy life and therefore could not have strictly meant that he was not good.
Levels of Goodness
Jesus, in order to reconcile us to the Father and qualify to be our faithful High Priest (Hebrews 4:14 - 15, 10:11 - 12), had to divest himself of many divine attributes. He had to, for example, give up his ability to eternally exist (John 1:4, 1Timothy 1:17) in order to suffer and die like a human.
One crucial characteristic of divinity the Lord gave up to become human was the impossibility to sin. God, as a spirit, cannot be tempted by evil (James 1:13) and cannot sin (see Hebrews 6:17 - 18, 1John 1:5). It was possible for Jesus, however, to succumb to the temptations of his human nature (Hebrews 4:15) and choose to disobey his Father. Knowing this, he constantly had to strive against a host of temptations in order to overcome them and not fall (Hebrews 5:7, 12:1 - 4).
Jesus' goodness or perfection, at the time he spoke to the young man, was not the same as his Father in heaven. Although Christ possessed a mix of divine and human nature, which made it possible for him to sin, God as a spirit cannot be tempted and is incorruptible. Only a member of the Godhead who exists as a spirit can be the unchangeable standard of good in the universe.
Conclusion
Jesus, throughout his life, did not trust his own judgment or behavior as they could be influenced by his human nature and lead to sin. He revealed that he constantly sought God's will and not his own (John 5:30). Jesus taught, spoke and behaved only as he had witnessed his Father speak and do (John 5:19 - 21, 8:28, 38, 10:37, 12:49 - 50). The Lord, in his response to the young man, was merely directing the rich ruler to the same standard of good he himself used.