Joh 2:23    Now when he was in Jerusalem at the passover, in the feast day, many believed in his name, when they saw the miracles which he did.

Joh 2:24    But Jesus did not commit himself unto them, because he knew all men,

Joh 2:25    And needed not that any should testify of man: for he knew what was in man.

Old John Gill explains this passage well.

John 2:24

But Jesus did not commit himself unto them,…. The sense according to some of the ancients is, that he did not commit the whole of the Gospel to them; he did not make known to them all his mind and will; this he only did to the twelve apostles, his special disciples and friends; nor was the time come, that he would make known, or have made known, the things concerning his person, office, obedience, sufferings, death, and resurrection from the dead: but rather the meaning is, that he did not trust himself with these persons, who believed in him, on the basis of his miracles; he did not take them into the number of his associates; he did not admit them to intimacy with him; nor did he freely converse with them, or make any long stay among them; but soon withdrew himself from hence, and went into other parts of Judea, and into Galilee:

because he knew all men: good and bad: all openly profane sinners, and all their actions; not only their more public ones, but those that are done in the dark, and which are the most secretly devised, and levelled against the saints; and he so knew them, as to bring them into judgment: and all good men, true believers; he knows their persons, as they are his Father’s choice, his gift of them to him, his own purchase, and as called by his grace; and so as to distinguish them at the last day, and give up the full account of every one of them to his Father: he knows the worst of them, the sin that dwells in them, their daily infirmities, their secret personal sins; their family sins, both of omission and commission; and their church sins, or which are committed in the house of God; and takes notice of them, so as to resent them, and chastise them for them; he knows the best of them, their graces, their faith, hope, love, patience, humility, self-denial, &c; he knows their good works, and all their weaknesses and their wants: and he knows all nominal professors, on what basis they take up their profession, and what trust they place in it; he can distinguish between grace and mere profession, and discern the secret lusts which such indulge, and the springs and progress of their apostasy: he knew all these men, that upon seeing his miracles, professed at this time to believe in him; he knew the hypocrisy and dissimulation of some of them; and he knew the notions they had of a temporal Messiah, and the temporal views they had in believing in him; and their design to set him up as a temporal prince, as some afterwards would have done: knew the flashy affections of others, who were like John’s hearers, that were pleased for a while; he knew what sort of faith it was they believed in him with, that it would not hold long, nor they continue with him; for he knew not only all persons, but παντα, “all things”, as some copies read here; see Joh 21:17.

John 2:25

And needed not that any should testify of man,…. Of this or the other man, that he was a good or a bad man; he needed no proofs to be made, or testimonies bore, or evidence given of men’s characters and actions; he was of quick understanding, and could distinguish at once between a wicked man and a good man; and so had the characteristic which the Jews require of the Messiah; for they rejected Bar Cozba from being the Messiah, and slew him, because he could not smell, referring to Isa 11:3, or discern a bad man from a good man (n); but this Jesus could do, without any external evidence:

for he knew what was in man; which none but the spirit of a man can know; his inward thoughts, the secrets of the heart; thus Christ knew the thoughts of the Scribes and Pharisees, Mat 9:4, being a discerner of the thoughts, and intents of the heart, Heb 4:12. This Apollonius Tyaneus, the ape of Christ, ascribed to himself (o); but is what is peculiar to God; and Christ being God, knows all that is in man; that there is no good in him naturally, nothing but what comes from his Father, is imparted by himself, or implanted by his Spirit; he knows the wickedness there is in man, that his heart is deceitful and desperately wicked, and full of all manner of iniquities; he knows in what condition all the and faculties of the souls of men are; what their affections are set upon, on earthly or heavenly things; whether there is any light in their understandings, or not; whether their wills are subdued and resigned to the will of God, or not; whether their minds and consciences are defiled, or their hearts are sprinkled from an evil conscience; in short, whether the internal good work of grace is begun upon their souls, or not; and he knows the secret springs of all actions, good and bad; all which prove his true and proper deity, and show him to be a suitable Saviour of sinners, and qualify him to be the Judge of the whole earth.

(n) T. Bab. Sanhedrin, fol. 93. 2. (o) Philostrat. Vit. Apollonii, l. 1. c. 13.