He went on to say, “This is why I told you that no-one can come to me unless the Father has enabled him.”
“This is why . . .” = Jesus had previously told them this so that they would understand when some did not believe.“Unbelief is to be expected apart from a divine miracle. It is impossible for anyone to come to Christ without the Father’s giving him the grace to do so. Left to himself the sinner prefers his sin. Conversion is always a work of grace.” (Morris 387)