God is all-knowing. But what, exactly, does that knowledge include? For one, God knows everything in the present.
For example, God knows all about you and how you act, think, and speak. In fact, He knows what you’ll say before you even say it:
You comprehend my path and my lying down,
And are acquainted with all my ways.
For there is not a word on my tongue,
But behold, O Lord, You know it altogether (Ps 139:3-4).
God knows your every word, and not for nothing. Jesus taught that you’ll be held accountable for every word you say:
“I say to you that for every idle word men may speak, they will give account of it in the day of judgment” (Matt 12:36).
But God not only knows your outward actions, He knows your inward thoughts, feelings, and dispositions:
“Thus you have said, O house of Israel; for I know the things that come into your mind” (Ezek 11:5b).
Sinners will not be comforted by the thought that God knows their every thought! I know it shames me. No wonder God could say:
“The heart is deceitful above all things,
And desperately wicked;
Who can know it?
I, the Lord, search the heart,
I test the mind,
Even to give every man according to his ways,
According to the fruit of his doings” (Jer 17:9-10).
How many thousands of thoughts do you have in a day? How many millions in a year? How many billions over a lifetime? How many trillions of thoughts does God know when you include all of humanity through all of history?
And God knows all of it!
The fact that God knows your thoughts, may not be comforting, but what is comforting is that God knows all about your physical needs for food, water, and clothing:
“For after all these things the Gentiles seek. For your heavenly Father knows that you need all these things” (Matt 6:32).
Indeed, you are so valuable to God that He knows every hair on your head:
“But the very hairs of your head are all numbered” (Matt 10:30).
God is aware of what is happening all over creation. In fact, Jesus said that not a single sparrow dies apart from God’s will:
Are not two sparrows sold for a copper coin? And not one of them falls to the ground apart from your Father’s will” (Matt 10:29).
If God wills those deaths, then He knows about them, too. To put that into perspective, I have read there are between 200 to 400 billion birds in the world. In the United States alone, an estimated 5 billion birds die every year, which comes to roughly 13.7 million birds dying every day. And God knows about every single one of them.
Life, death, actions, thoughts, and words—God knows it all—about everyone and everything.
Hence, God is omniscient.