There are two similar passages in Mark where someone asks Jesus about righteousness and the commandments, and when you put the two passages together, an interesting parallel emerges. Consider first Mark 12:28-31:
One of the scribes came and heard them arguing, and recognizing that [Jesus] had answered them well, asked Him, “What commandment is the foremost of all?” Jesus answered, “The foremost is, ‘Hear, O Israel! The Lord our God is one Lord; and you shall love the Lord your God with all your heart, and with all your soul, and with all your mind, and with all your strength.’ The second is this, ‘You shall love your neighbor as yourself.’ There is no other commandment greater than these.”
When the scribe agrees, Jesus says he is “not far from the kingdom of God.” But if “Love the Lord your God with all your heart, and with all your soul, and with all your mind, and with all your strength” is the greatest commandment, why would Jesus leave out that commandment in Mark 10:17-20?
As [Jesus] was setting out on a journey, a man ran up to Him and knelt before Him, and asked Him, “Good Teacher, what shall I do to inherit eternal life?” And Jesus said to him, “Why do you call Me good? No one is good except God alone. You know the commandments, ‘Do not murder, Do not commit adultery, Do not steal, Do not bear false witness, Do not defraud, Honor your father and mother.’” And he said to Him, “Teacher, I have kept all these things from my youth up.”
Maybe Jesus didn’t leave it out, for He goes on in verse 21:
Looking at him, Jesus felt a love for him and said to him, “One thing you lack: go and sell all you possess and give to the poor, and you will have treasure in heaven; and come, follow Me.” But at these words he was saddened, and he went away grieving, for he was one who owned much property.
Does Mark 12 clarify Mark 10? Could the one thing the rich man lacked have been the greatest thing: loving Jesus with all his heart, soul, mind, and strength, above all other things he loved (and in the process, loving his neighbor as himself by giving his possessions to the poor)? Was Jesus preparing the man to make this connection between the greatest commandment and following Him by calling attention to the fact that He had the goodness of God? Is there any other way to explain Jesus leaving out what He considered to be the greatest commandment of all?
It gets even more interesting when you consider that immediately after Jesus commends the scribe in Mark 12 for acknowledging that "Love the Lord your God" is the greatest commandment, He hints at His deity yet again, saying:
How is it that the scribes say that the Christ is the son of David? David himself said in the Holy Spirit, “The Lord said to my Lord, ‘Sit at My right hand, until I put Your enemies beneath Your feet.’” David himself calls Him “Lord”; so in what sense is He his son?
So in Mark 10, we have a hint of Jesus’ deity (“Why do you call Me good?”) and a command to love Him more than all possessions, with no mention of the “love God” commandment. Then in Mark 12, we hear that loving God above all else is the greatest commandment, followed by a hint of the Messiah’s deity.
It does seem like these closely related passages connect Jesus’ command to follow Him with the greatest commandment.