What is Required in the First Commandment?

The First Commandment requires us to know and acknowledge God to be only true God, and our God; and to worship and glorify Him accordingly.

1 Chronicles 28:9 (NASB)
As for you, my son Solomon, know the God of your father, and serve Him with a whole heart and a willing mind; for the LORD searches all hearts, and understands every intent of the thoughts. If you seek Him, He will let you find Him; but if you forsake Him, He will reject you forever.

Deuteronomy 26:17 (NASB)
You have today declared the LORD to be your God, and that you would walk in His ways and keep His statutes, His commandments and His ordinances, and listen to His voice.

Matthew 4:10 (NASB)
Then Jesus *said to him, “Go, Satan! For it is written, ‘YOU SHALL WORSHIP THE LORD YOUR GOD, AND SERVE HIM ONLY.’”