Exodus 20:25

Defiled; because done in opposition to God's order, who required, on this occasion, the utmost simplicity, to prevent any undue veneration. Iron was not used about the tabernacle or temple, as brass was more common. Altars raised in haste, like that, Deuteronomy xxvii. and Josue viii. 30, and that which was designed for the ratification of the covenant, (chap. xxiv. 4,) were required to be of this construction, unpolished and simple, as was the altar erected, 1 Machabees iv. 47. But other altars were not built after this model. (Calmet)