Psalm 44:21

"Shall not God search this out? for he knoweth the secrets of the heart."

Cross References (ranked by relevance)

I the LORD search the heart, I try the reins, even to give every man according to his ways, and according to the fruit of his doings.

Jeremiah 23:24

Can any hide himself in secret places that I shall not see him? saith the LORD. Do not I fill heaven and earth? saith the LORD.

Job 31:4

Doth not he see my ways, and count all my steps?

Ecclesiastes 12:14

For God shall bring every work into judgment, with every secret thing, whether it be good, or whether it be evil.

1 Corinthians 4:5

Therefore judge nothing before the time, until the Lord come, who both will bring to light the hidden things of darkness, and will make manifest the counsels of the hearts: and then shall every man have praise of God.

Romans 2:16

In the day when God shall judge the secrets of men by Jesus Christ according to my gospel.

Job 31:14

What then shall I do when God riseth up? and when he visiteth, what shall I answer him?

Revelation 2:23

And I will kill her children with death; and all the churches shall know that I am he which searcheth the reins and hearts: and I will give unto every one of you according to your works.