He did not need any testimony about man, for He knew what was in a man.

Deuteronomy 31:21
And when many troubles and afflictions have come upon them, this song will testify against them, because it will not be forgotten from the lips of their descendants. For I know their inclination, even before I bring them into the land that I swore to give them."

1 Kings 8:39
be heard by You from heaven, Your dwelling place. And may You forgive and act, and repay each man according to all his ways, since You know his heart--for You alone know the hearts of all men--

Isaiah 11:3
And He will delight in the fear of the LORD. He will not judge by what His eyes see, and He will not decide by what His ears hear,

Matthew 9:4
But Jesus knew what they were thinking and said, "Why do you harbor evil in your hearts?

John 1:42
Andrew brought him to Jesus, who looked at him and said, "You are Simon son of John. You will be called Cephas" (which is translated as Peter).

John 1:47
When Jesus saw Nathanael approaching, He said of him, "Here is a true Israelite, in whom there is no deceit."

John 6:61
Aware that His disciples were grumbling about this teaching, Jesus asked them, "Does this offend you?

John 6:64
However, there are some of you who do not believe." (For Jesus had known from the beginning which of them did not believe and who would betray Him.)

John 13:11
For He knew who would betray Him. That is why He said, "Not all of you are clean."

And needed not that any should testify of man: for he knew what was in man.