How did Saul break the commandment of the Lord in I Samuel 13:11-14? He was offering to God.
Saul did make an offering to God, but he did not do it in the manner which God wanted offerings done. It did not matter that Saul felt he was compelled to make an offering (I Samuel 13:12). It didn't matter that it was offered to God. The fact is that Saul was acting without authority, which is what the word "iniquity" means. He was specifically told, "You shall go down before me to Gilgal; and surely I will come down to you to offer burnt offerings and make sacrifices of peace offerings. Seven days you shall wait, till I come to you and show you what you should do" (I Samuel 13:8). Saul decided he couldn't wait. In addition only priests or prophets were allowed to give offerings to God (Leviticus 7:8), and Saul was neither.
This serves as warning to people today. We can't expect God to accept whatever we decide to offer Him. "Not everyone who says to Me, 'Lord, Lord,' shall enter the kingdom of heaven, but he who does the will of My Father in heaven. Many will say to Me in that day, 'Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and done many wonders in Your name?' And then I will declare to them, 'I never knew you; depart from Me, you who practice lawlessness!'" (Matthew 7:21-23). Worship is defined by God, not man.