Because Ephraim hath made many altars to sin, altars shall be unto him to sin.
Because Ephriam hath made many altars to sin, altars shall be unto him to sin. God, in righteous retribution, gives them up to their own way: the sin becomes its own punishment, (Proverbs 1:31).
Many altars - in opposition to God's law, which commanded that the temple at Jerusalem was to be the only place for offering sacrifices (Deuteronomy 12:5-6; Deuteronomy 12:13-14).
To sin ... to sin - their altars, which were "sin" (whatever religious intentions they might plead), should be treated as such, and be the source of their punishment (1 Kings 12:30, "And this thing (the calf-worship) became a sin;" 1 Kings 13:34). The many altars of Ephraim, which were in fact only so many sins, shall be proved to be but sins by their results-namely, Ephraim's punishment.