John Gill

Why do ye not understand my speech?.... Language, idiom, dialect, and form of speaking, in a figurative way; for they did not know what he meant by liberty, and bondage, and by having another father than Abraham, or by his own procession and coming forth from God: even because ye cannot hear my word; as they had no spiritual discerning and understanding of the doctrine of Christ, which showed them to be carnal, and natural men, and not regenerate ones, and the children of God; so they had an aversion to it, and could not bear to hear it.