John Wesley on 2 Kings 18:4

Serpent - The most of them, or such as the people most frequented: for all were not taken away, chap.23:13,14, tho' his own father had set them up. We must never dishonour God, in honour to our earthly parents. Brazen serpent - Which had been hitherto kept as a memorial of God's mercy; but being now commonly abused to superstition, was destroyed. To it - Not doubtless as to a god, but only as to an instrument of God's mercy, by and through which, their adoration was directed to God, and given to that only for God's sake. Nehushtan - He said, this serpent, howsoever formerly honoured, and used by God as a sign of his grace, yet now it is nothing but a piece of brass which can do you neither good nor hurt.