The Bible declares that there is but one God. “I am God, and there is no other; I am God, and there is none like Me” (Isaiah 46:9; see also Malachi 2:10). The God of the Bible is the true God (2 Chronicles 15:3; Jeremiah 10:10). He is distinguished from “other gods” (Exodus 23:13; Judges 2:12; 1 Samuel 8:8; 1 Kings 9:9, etc.) or “foreign gods” (Genesis 35:2, 4; Deuteronomy 32:16; Joshua 24:20, 23; Judges 10:16; 1 Samuel 7:3; 2 Chronicles 14:3; 33:15; Jeremiah 5:19) by the fact that he created heaven and earth (Jeremiah 10:11; 1 Chronicles 16:25-26; Psalm 96:4-5).
The true God has power, whereas other so called gods have none. During early biblical times many people did not believe in nor serve the one true God. Although Abraham, Isaac, and Jacob believed in and served the creator God (Exodus 3:6; 15-16; 4:5; Matthew 22:32; Romans 4:3, 17; Galatians 3:6; James 2:23), neither his father Terah nor his brother Nahor believed in that God (Genesis 11:26; Joshua 24:2). During Jacob’s lifetime, some of his own family worshipped foreign gods (Genesis 31:30, 32; 35:2, 4). When the Israelites came out of Egypt, they were commanded to have no other gods (Exodus 20:3; Deuteronomy 5:7; see also Exodus 34:13-14; Deuteronomy 11:16, etc.). God is a jealous God (Exodus 20:5; 34:14; Matthew 6:24).
They were told many times that to worship and serve other gods would be catastrophic (Exodus 23:33; Deuteronomy 7:4; 8:19; 30:17-18; Joshua 23:16; 24:20). Even so, after Moses ascended Mt. Sinai to receive the law from God, the Israelites clamored for gods (Exodus 32:1, 23). Aaron, Moses brother and also the Israelite high priest, molded a calf of gold and set a day for them to worship it (Exodus 32:2-6). Before coming into the Promised Land, Israel was charged not to worship or serve the gods of the land they would be conquering (Exodus 23:34; 34:12-17; Leviticus 19:4; Deuteronomy 6:14; 7:16; etc.)