The usual suspects include "Do not commit adultery," "Have no other gods before me," and "Love one another." The next group includes whatever commands you know you have violated, in which case they only feel as if they appear on every page of Scripture.
The actual answer is "Do not be afraid."
Here is a sampling (italics added) of its over three hundred occurrences.
After this, the word of the LORD came to Abram in a vision: "Do not be afraid, Abram. I am your shield, your very great reward" (Gen 15:1).
God heard the boy crying, and the angel of God called to Hagar from heaven and said to her, "What is the matter, Hagar? Do not be afraid; God has heard the boy crying as he lies there" (Gen 21:17).
That night the LORD appeared to him and said, "I am the God of your father Abraham. Do not be afraid, for I am with you" (Gen. 26:24).
"I am God, the God of your father," he said. "Do not be afraid to go down to Egypt, for I will make you into a great nation there" (Gen. 46:3).
The LORD said to Moses, "Do not be afraid of him, for I have handed him over to you, with his whole army and his land" (Num. 21:34).
The angel of the LORD said to Elijah, "Go down with him; do not be afraid of him" (2 Kings 1:15).
He said: "Listen, King Jehoshaphat and all who live in Judah and Jerusalem! This is what the LORD says to you: 'Do not be afraid or discouraged because of this vast army. For the battle is not yours, but God's'" (2 Chron. 20:15).
Be careful, keep calm and don't be afraid. Do not lose heart because of these two smoldering stubs of firewood -- because of the fierce anger of Rezin and Aram and of the son of Remaliah (Isa. 7:4).
"Do not be afraid, O worm Jacob, O little Israel, for I myself will help you," declares the LORD, your Redeemer, the Holy One of Israel (Isa. 41:14).
Do not tremble, do not be afraid. Did I not proclaim this and foretell it long ago? You are my witnesses. Is there any God besides me? No, there is no other Rock; I know not one (Isa. 44:8).
Do not be afraid; you will not suffer shame. Do not fear disgrace; you will not be humiliated. You will forget the shame of your youth and remember no more the reproach of your widowhood (Isa. 54:4).
"Do not be afraid of them, for I am with you and will rescue you," declares the LORD (Jer. 1:8).
Then he continued, "Do not be afraid, Daniel. Since the first day that you set your mind to gain understanding and to humble yourself before your God, your words were heard, and I have come in response to them" (Dan. 10:12).
Do not be afraid of those who kill the body but cannot kill the soul (Matt. 10:28).
But Jesus immediately said to them: "Take courage! It is I. Don't be afraid" (Matt. 14:27).
Then Jesus said to them, "Do not be afraid. Go and tell my brothers to go to Galilee; there they will see me" (Matt. 28:10).
Peace I leave with you; my peace I give you. I do not give to you as the world gives. Do not let your hearts be troubled and do not be afraid (John 14:27).
Now envision pages more of such references. Do you get the sense that God is alert to your fears? The sheer number of times He speaks to your fears says that He cares much more than you know.
~ Adapted from Running Scared by Ed Welch