"Then said they unto him, What shall we do, that we might work the works of God?" (John 6:28)
This question is often asked by people who try to work their way into heaven. It was also asked in various ways by men in the New Testament, and it is vitally important to get the correct answer to such questions there, and nowhere else.
For example, a rich young ruler once asked Jesus, "What shall I do that I may inherit eternal life?" Jesus answered, "Go thy way, sell whatsoever thou hast, and give to the poor . . . and come, take up the cross, and follow me" (Mark 10:17, 21). That is, there is nothing of his own that one can bring to Christ to earn salvation; one must simply be willing to yield himself fully to Christ.
A lawyer had asked Jesus the same question, "tempting Him." This time, His answer was, "Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy strength, and with all thy mind; and thy neighbour as thyself" (Luke 10:27). But this standard is humanly unattainable by any child of Adam, so in effect, the lawyer was told it was impossible for him to do anything himself to inherit eternal life.
When the crowd asked Peter on the day of Pentecost, "pricked in their heart" because they had crucified Christ, "What shall we do?" Peter answered, "Repent, and be baptized . . . in the name of Jesus Christ for the remission of sins" (Acts 2:37-38). What they had to "do" was an inward act of repentance and faith toward Christ and an outward public testimony demonstrating the reality of that inward change of heart and mind.
Years later at Philippi, a jailer asked Paul the apostle one night, "What must I do to be saved?" The answer was simply, "Believe on the Lord Jesus Christ, and thou shalt be saved" (Acts 16:30-31). HMM