What is the duty which God requires of man?

The duty which God requires of man is obedience to His revealed will.

God does not require religious works. The religion of old involved burnt offerings with yearling calves, rams and oil, but this is not what God requires of man. Nor does God require our children. (Micah 6:6-7) So, if God does not require of man the fruit of our labors or the fruit of of our bodies, what does God require of man?

Micah 6:8 (NASB)
“He has told you, O man, what is good;
And what does the LORD require of you
But to do justice, to love kindness,
And to walk humbly with your God?”

God is not asking to be appeased through gifts offered to Him. The only thing that God requires of redeemed man is to be just, kind and humble.