2 Tim 1:12
For the which cause I also suffer these things: nevertheless I am not ashamed: for I know whom I have believed, and am persuaded that he is able to keep that which I have committed unto him against that day.
A Spiritual knowing of Christ is an condition for believing in Him, and this knowing must be by revelation, for Jesus said here Matt 11:27
27 All things are delivered unto me of my Father: and no man[by nature] knoweth the Son, but the Father; neither knoweth any man the Father, save the Son, and he to whomsoever the Son will reveal him.
Only those whom the Father reveals the Son to know Him, as it was with Peter here in this narrative Matt 16:15-17
15 He saith unto them, But whom say ye that I am?
16 And Simon Peter answered and said, Thou art the Christ, the Son of the living God.
17 And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven.
Peters knowledge of Christ as being the Christ/ Messiah, the Son of the Living God was not something he could have known by nature, in flesh and blood, but by Divine revelation.
And so as one writer once said, John Gill :
"an unknown Christ cant be the object of our Faith "
Such knowledge of Christ by revelation is an imperative before we believe on Christ for Salvation matters !
How can you explain the Sheep hearing His voice and knowing it, in order to follow Him Jn 10:2-5
But he that entereth in by the door is the shepherd of the sheep.
3 To him the porter openeth; and the sheep hear his voice: and he calleth his own sheep by name, and leadeth them out.
4 And when he putteth forth his own sheep, he goeth before them, and the sheep follow him: for they know his voice.
5 And a stranger will they not follow, but will flee from him: for they know not the voice of strangers.
This knowing of Christ is a New Covenant Blessing Heb 8:11
11 And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest.
Christ Sheep is promised that they shall know Him Jn 10:14
14 I am the good shepherd, and know my sheep, and am known of mine.
Because as the good shepherd He layed down His Life for them Jn 10:11
11 I am the good shepherd: the good shepherd giveth his life for the sheep.
It would be a travesty if the ones the Good Shepherd gave His Life for, never came into a Saving Knowledge of Him !
The Sheep are able to know Him to a degree, to believe and follow Him because they have His Spirit given them, which marks them as His Rom 8:9
9 But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.
So His Sheep which hear His voice and knows His voice, must have had the Spirit of Christ in them Jn 10:2-4
2 But he that entereth in by the door is the shepherd of the sheep.
3 To him the porter openeth; and the sheep hear his voice: and he calleth his own sheep by name, and leadeth them out.
4 And when he putteth forth his own sheep, he goeth before them, and the sheep follow him: for they know his voice.
Having His Spirit is imperative to show that we belong to Christ, and so we can hear His voice in the Gospel !