The First Commandment: You shall have no other gods.
When God brought his people out of Egypt under Moses' leadership, he wanted them to know his rules, the laws he would expect them to follow and live by. On Mount Sinai God gave Moses the Ten Commandments, which would show his people how to live. The First Commandment is worth noting for two reasons: first, this commandment is the foundation for all the others; and second, this commandment was the first one the Israelites disobeyed, even before they received it.
God often makes it clear in the Bible that he expects to have first place in man's life. As the Creator of the world and everything in it, as the Creator of man himself, God has every right to demand of all human beings, "You shall have no other gods." God points out that "There is no god besides me" (Deuteronomy 32:39), and as the only God he expects perfect love and perfect obedience from all human beings.
Martin Luther explained that the First Commandment means that "We should fear, love and trust in God above all things." Anything which you love and trust above everything, which you depend on for your life and security, is your God. The God who created us expects that perfect love and trust from us. Unfortunately, we're often better at creating our own gods. We often fear, love and trust in ourselves, or our money, or anything else rather than God, and for our unfaithfulness we deserve God's punishment.
The Israelites had that problem too. While Moses was on Mount Sinai receiving the Ten Commandments, the Israelites were at the foot of the mountain making a new god for themselves. The Israelites feared that God and Moses had deserted them, so they created a new god--a golden calf. God gave Moses the bad news about the Israelites and their idol, and announced his judgment on the Israelites: "Now leave me alone so that my anger may burn against them and that I may destroy them."
Moses didn't want to see his people destroyed for their sin. Even though the people of Israel deserved God's anger and punishment, Moses pleaded with God not to destroy them. God listened. He did not destroy the Israelites as they deserved.
We can be glad that God does not simply punish us as we deserve for our sins and unfaithfulness to him. The Bible shows us that God is our loving Father who does not want to see us punished as we deserve. God sent Jesus to take our punishment away. Jesus saved us from the punishment we deserve for our disobedience by suffering that punishment himself. By suffering and dying on the cross, Jesus paid for our sins and opened the door to heaven for us. Through Jesus, God makes it possible for us to fear, love and trust in him above all things, and gives us good reason to do it: "We love because he first loved us" (1 John 4:19).
God commands, "You shall have no other gods." There's no reason to have any other gods--the God of the Bible has done everything for us already. He gives us life and livelihood. Most importantly he forgives our sins and rescues us from the punishment we deserve for disobeying him.