Deuteronomy — Chapter 4

You shall not add to the word that I speak to you, neither shall you take away from it. Lapide: This forbids private interpretation and novel doctrine; the canon of Scripture is closed, and tradition fixes its sense. Heretics add and subtract at will.

The Lord thy God is a consuming fire. Lapide notes this text is cited at Heb. 12:29, and signifies that God destroys sin and sinners by the fire of His justice, while the same fire purifies and illuminates His saints as with divine charity.

I call heaven and earth to witness against you this day. Moses makes creation itself a witness against Israel's apostasy; Lapide notes the same rhetorical figure is used in the Canticle of Moses (ch. 32) and the prophets: all creatures testify against those who abandon their Creator.

But if from thence thou seek the Lord thy God, thou shalt find him: if thou seek him with all thy heart and with all thy soul. God promises that even in exile and captivity, sincere conversion of heart will obtain pardon. No sin is too great, no exile too far, if the will returns to God.

That thou mightest know the Lord, he is God, and there is no other beside him. Lapide: This is the fundamental article of faith—monotheism—against which all idolatry offends. God is not merely one among many, but the only true Being from Whom all creation depends.