What prevents the Jews from coming to Jesus and believing in him, therefore, is not that salvation is not intended for them, but that they do not want to receive it in the manner in which God would give it to them, namely by their coming to Jesus. For “everyone who has and learned from the Father comes to me.” Hence the remarkable fact that Jesus would have the Jews understand their unbelief and powerlessness (“no one can . . .”) in light of a divine prophecy of salvation. The very thing that they reject in hi as self-willed conceit is what God wants to give them in him. “Unless the Father draws him” (vs. 44) therefore applies to them, not only negatively but also positively.
“No one can come to me” is intended to take away the illusion that “coming to Jesus” is a matter about which one can freely decide on the basis of one’s own “knowledge” and possibilities. This observation keeps coming back in the Gospel (cf. 1:12, 13; 3:3ff.; 5:44); one might call it one of the fundamental thoughts.
Ridderbos, Herman N. The Gospel according to John: A Theological Commentary. Grand Rapids, Mich.: W.B. Eerdmans Pub., 1997. Print. (p233)