John Gill Commentary John 8:19

"They said therefore unto him, Where is thy Father? Jesus answered, Ye know neither me, nor my Father: if ye knew me, ye would know my Father also." — John 8:19 (ASV)

Then said they unto him, where is your Father ?
&c.] The Persic version adds, "show [him] unto us": produce this witness boasted of, let us see him; this they said in a sneering, taunting, and insulting manner; where is your Father? what! he is in Galilee; fetch him from thence; it is Joseph the carpenter you mean; a goodly witness indeed!

Jesus answered, you neither know me nor my Father; if you had known
me, you should have known your Father also ;
they did not know the divine original of Christ, that he was the Son of God, and that God was his Father; they greatly boasted of their knowledge of God, but they knew him not; their ignorance of Christ showed it: the knowledge of both go together, and which is life eternal; nor can any truly know the one, without the other.

Where the one is known, the other will be also; Christ is the brightness of his Father's glory, and the express image of his person: so that he that has seen the one, must know the other; and indeed, no one can know the Father, but he to whom the Son reveals him: this was a severe mortification to these men of knowledge.