According to Mark 10:21, there was still "one thing" the man lacked. There was one primary thing he had not done. There was one thing holding him back from being "perfect" or complete in his pursuit of eternal life (cf. James 2:10). "If you want to be perfect, go, sell what you have and give to the poor, and you will have treasure in heaven; and come, follow Me" (Matt. 19:21).
Jesus instructed the rich, young ruler - "Sell all that you have" (Luke 18:22). This last requirement tested whether the man loved God with all his heart or just part of it. It was essentially a summation of the first four commandments given on Mt. Sinai (cf. Exo. 20:1-11). After selling everything, he was to give the money to the poor. This requirement may seem harsh, but it was not a command reserved only for this man. The true disciples of Jesus at that time had already "left all" to follow Him (cf. Matt. 19:27; Phil. 3:7-9).
If this rich man was willing to obey, he would have "treasure in heaven." One must renounce earth to receive heaven. Certainly heaven is worth the sacrifice and the exchange is a profitable one! If any man has a heart that is fixed on Earth, so that he hesitates to make the exchange, he is not yet fit for God's kingdom. The mere giving up of his possessions would not save the rich, young ruler. That was only a test of his character and of his fitness for discipleship. Following Jesus is what would save him.
This narrative teaches us that even the very best of men must give up self in order to be saved. Just because one keeps many of God's teachings properly does not mean that he will enter into eternal life. One may live a virtuous life and fulfill all the requirements of moral law (as this man did), yet lack the true Christian spirit (i.e., self-denial and self-sacrifice). If a person has a higher allegiance to anything or anyone other than God, then such a one is in violation of the greatest commandment and will not be saved (cf. Matt. 22:37,38).
Jesus does not require those with possessions and property to sell all that they have today (for one cannot journey with Him over the Palestinian hills anymore), but He does demand that His followers use all that they have for His honor and glory (cf. Matt. 25:27; I Cor. 16:1,2; Eph. 4:28; I Tim. 5:8; 6:17-19). The Lord demands that we "deny" ourselves and "count the cost" (Matt. 16:24; Luke 14:28). For example, Zacchaeus "was rich" (Luke 19:2) and agreed to give only half of his goods to feed the poor. Jesus nevertheless said to him - "Today salvation has come to this house" (19:8,9). Unlike this rich ruler, Zacchaeus was master over his possessions and not a slave to them.
"But when the young man heard that saying, he went away sorrowful, for he had great possessions" (Matt. 19:22). The fact that the rich young ruler went away sorrowful is a tragedy, but certainly it is better to go away sorrowful than angry. This indicates that he was not one of the most hardened of the rich. If this man was exceedingly greedy, had little concern for eternal life, or had little confidence in Jesus, the chances are likely that he would have went away offended at Jesus' demand (instead of sorrowful). The rich, young ruler's sorrow indicates that he had a respect for Jesus' authority. However, his love for money and worldly possessions was greater.
In spite of the fact that Jesus greatly loved this man, He would not modify His demand in order to avoid losing him. No one today has the right to soften God's teaching (i.e., compromise with error) in order to please men, make "converts," or prevent the loss of a "disciple."