Good works are an integral part of the Christian life. However, they are not the cause but the result of having been justified before God. The heavenly rewards which He bestows upon us are dependent on our good works. The author seems to conflate the terms gift and reward. Justification before God is not something we can earn on the basis of good works that we perform, even in part. It is an unmerited grace of God.
"But this parable doesn’t teach the sufficiency of faith for justification; it teaches the necessity of repentance...When Jesus explains this parable, he does not say the tax collector was justified rather than the Pharisee because the former did not rely on works for his justification. Instead, the Pharisee was not justified because he was guilty of the sin of pride, whereas the tax collector was humble and recognized his need to repent. Jesus even explains why the tax collector rather than the Pharisee was justified: “For every one who exalts himself will be humbled, but he who humbles himself will be exalted” (Luke 18:14)—indicating it is the tax collector’s humble, repentant attitude that is the distinguishing factor."
Why cannot the parable of the Rich Man and Tax Collector address both faith as being the instrument of justification and the necessity of repentance from sin? If faith is not enough to bring about our justification in the sight of God, then it would not make any sense for Jesus Christ to have said that the humble tax collector went home justified. The only thing that he had was faith. Moreover, the text informs us that the rich man trusted in his good works to get right with God. He pointed to his deeds as the basis of his righteousness. The rich man went to his house condemned. Thus, Christ plainly taught that no one should rely on his or her own good works in order to be justified before God. The Pharisee is an illustration of the ultimate failure of a system of works righteousness. Such efforts get to our heads and thereby insult God in His glory.
"In fact, in the next chapter an actual tax collector, Zacchaeus, repents of his wrongdoings and seeks forgiveness from Jesus. It is only after Zacchaeus declares he will pay back everyone he defrauded that Jesus tells him, “Today salvation has come to this house” (Luke 19:9)."
The desire of Zacchaeus to make restitution to the people that he previously stole from serves as evidence of him having truly repented of his sins. Good works are a consequence or product of a saving faith.
"Finally, MacArthur cites John 5:24, because Jesus said, “He who hears my word and believes him who sent me, has eternal life; he does not come into judgment, but has passed from death to life.” But just four verses later Jesus says that, at the final judgment, “All who are in the tombs will hear his voice and come forth, those who have done good, to the resurrection of life, and those who have done evil, to the resurrection of judgment.”
John 5:24 speaks of having eternal life in the present tense or being immediately in one's own possession at the moment of conversion. D.A. Carson, in the NIV Zondervan Study Bible, says the following in regards to the meaning of this text: