Joh 6:29 Jesus told them, This is the only work God wants from you: Believe in the One He has sent.
If you want to go with this that is good also. It says faith in Jesus is the work of God, not our own ability. But it is still the ONE thing that is needed.
(MKJV) Jesus answered and said to them, This is the work of God, that you believe on Him whom He has sent.
And to believe in Him is to believe that we need to keep the Commandments:
Not everyone who says to me, Lord, Lord, will enter the kingdom of heaven, but only the one who does the will of my Father in heaven. (Matt. 7:21)Jesus came to call us out of our sins and selfishness, and back to union with God through our love of Him:[Jesus] answered him, Why do you ask me about the good? There is only One who is good. If you wish to enter into life, keep the commandments. (Matt. 19:17)
This is the greatest and the first commandment. The second is like it: You shall love your neighbor as yourself. The whole law and the prophets depend on these two commandments. (Matt. 22:38-40)
Is the book of James in your Bible? How often have you re-read it?