Paul had a deep understanding of God’s grace, quite possibly as a result of his miraculous conversion that saw him change from a violent enforcer of religious orthodoxy to a missionary of grace. He knew about trying to work for God’s favour, but he found a better way.
Ephesians 2:8-10 God saved you by his grace when you believed. And you can’t take credit for this; it is a gift from God. Salvation is not a reward for the good things we have done, so none of us can boast about it. For we are God’s masterpiece. He has created us anew in Christ Jesus, so we can do the good things he planned for us long ago.
A different translation of these verse is more widely quoted, but it says the same thing:
Ephesians 2:8-10 For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast. For we are His workmanship, created in Christ Jesus for good works, which God prepared beforehand that we should walk in them.
And what are those ‘good works’ He has prepared for believers? It’s everything He commands us to do in His Word. The works been likened to rebuilding a house after a fire.