1 Corinthians 15:10, “But by the grace of God I am what I am: and his grace which was bestowed upon me was not in vain; but I laboured more abundantly than they all: yet not I, but the grace of God which was with me.”
Every one of us are what we are in the natural by our birth, by our training, and by our experiences. We are also something by the grace of God. Because of this, it is not unjust of God to require anything of us. Whatever God requires, His grace empowers and enables us to do it. His grace makes us enough or sufficient for the obligation or responsibility (Acts 1:8, Ephesians 2:10).
The Cross was the starting point of grace in our lives but it is also the starting point of doing good works. Good works begin at the Cross. We were created in Christ Jesus unto good works or that good works would result (Eph. 2:10). For all the work we do, there is empowering grace for it (See Acts 14:2-3). All Christians are given gifts of grace for service (Romans 12:6) and no one is given grace to sit or to do nothing.