There is simply no where else to go with this if you don't believe God is omniscient. I'm seriously shocked to learn some Christians don't believe that.
God is Omniscient - Old Testament Evidence
“Remember the former things, those of long ago; I am God, and there is no other; I am God, and there is none like me. I make known the end from the beginning, from ancient times, what is still to come. I say: My purpose will stand, and I will do all that I please” (
Isaiah 46:9-10).
“Who can fathom the Spirit of the LORD, or instruct the LORD as his counselor? Whom did the LORD consult to enlighten him, and who taught him the right way? Who was it that taught him knowledge, or showed him the path of understanding?” (
Isaiah 40:13-14).
“Before a word is on my tongue you know it completely, O LORD” (
Psalm 139:4).
“O LORD, you have searched me and you know me. You know when I sit and when I rise; you perceive my thoughts from afar. You discern my going out and my lying down; you are familiar with all my ways” (
Psalm 139:1-3).
“My frame was not hidden from you when I was made in the secret place, when I was woven together in the depths of the earth. Your eyes saw my unformed body; all the days ordained for me were written in your book before one of them came to be. How precious to me are your thoughts, God! How vast is the sum of them! Were I to count them, they would outnumber the grains of sand—when I awake, I am still with you” (
Psalm 139:15-16).
“Can anyone teach knowledge to God, since he judges even the highest?” (
Job 21:22).
“He determines the number of the stars and calls them each by name. Great is our Lord and mighty in power; his understanding has no limit” (
Psalm 147:4-5).
“And you, my son Solomon, acknowledge the God of your father, and serve him with wholehearted devotion and with a willing mind, for the LORD searches every heart and understands every desire and every thought. If you seek him, he will be found by you; but if you forsake him, he will reject you forever” (
1 Chronicles 28:9).
“Do you know how the clouds hang poised, those wonders of him who has perfect knowledge?” (
Job 37:16).
“From heaven the LORD looks down and sees all mankind; from his dwelling place he watches all who live on earth—he who forms the hearts of all, who considers everything they do” (
Psalm 33:13-15).
God is Omniscient – The New Testament Evidence
“Oh, the depth of the riches of the wisdom and knowledge of God! How unsearchable his judgments, and his paths beyond tracing out!” (
Romans 11:33).
“Nothing in all creation is hidden from God’s sight. Everything is uncovered and laid bare before the eyes of him to whom we must give account” (
Hebrews 4:13).
“Indeed, the very hairs of your head are all numbered. Don’t be afraid; you are worth more than many sparrows” (
Luke 12:7).
“Whenever our hearts condemn us. For God is greater than our hearts, and he knows everything” (
1 John 3:20).
“Are not two sparrows sold for a penny? Yet not one of them will fall to the ground apart from the will of your Father. And even the very hairs of your head are all numbered” (
Matthew 10:29-30).