Deuteronomy 19:18

And the judges shall make diligent inquiry: and, behold, if the witness is a false witness, and has testified falsely against his brother;

Deuteronomy 13:14

Then shall you inquire, and make search, and ask diligently; and, behold, if it be truth, and the thing certain, that such abomination is wrought among you;

Deuteronomy 17:4

And it be told you, and you have heard of it, and inquired diligently, and, behold, it is true, and the thing certain, that such abomination has been done in Israel:

2 Chronicles 19:6-7

And said to the judges, Take heed what you do: for you judge not for man, but for the LORD, who is with you in the judgment.

Job 19:16

I called my servant, and he gave me no answer; I entreated him with my mouth.

Treasury of Scripture Knowledge

Summary

And the judges shall make diligent inquisition: and, behold, if the witness be a false witness, and hath testified falsely against his brother;

Bible References

Diligent

Deuteronomy 13:14
Then shall you inquire, and make search, and ask diligently; and, behold, if it be truth, and the thing certain, that such abomination is wrought among you;
Deuteronomy 17:4
And it be told you, and you have heard of it, and inquired diligently, and, behold, it is true, and the thing certain, that such abomination has been done in Israel:
2 Chronicles 19:6
And said to the judges, Take heed what you do: for you judge not for man, but for the LORD, who is with you in the judgment.
Job 19:16
I called my servant, and he gave me no answer; I entreated him with my mouth.

General references

Deuteronomy 5:20
Neither shall you bear false witness against your neighbor.
Deuteronomy 25:1
If there is a controversy between men, and they come unto judgment, that the judges may judge them; then they shall justify the righteous, and condemn the wicked.
John 7:51
Does our law judge any man, before it hears him, and knows what he does?