John Calvin Commentary Deuteronomy 32:34

"Is not this laid up in store with me, Sealed up among my treasures?" — Deuteronomy 32:34 (ASV)

Is not this laid up in store with me? Although some explain this verse as relating to their punishments—as if God asserted that various kinds of them were laid up with Him, which He could produce whenever He pleased—it is more correct to understand it as referring to their crimes. We are well aware that the ungodly, when God withholds His severity, promise themselves impunity, as if His forbearance were a kind of connivance. Unless, therefore, He immediately lifts up His hand to chastise them, they imagine that all recollection of their crimes has vanished from His memory. Consequently, the prophets often remind hypocrites of the day of visitation, so that they may not suppose that they have gained anything by the delay. For this reason, Jeremiah says that

the sin of Judah is written with an iron pen
and with the point of a diamond, (Jeremiah 17:1).

Moses employs a different figure: although God may not appear as an immediate avenger, still their sins are stored up in His treasures and will be brought to light by Him at the appropriate time. From this we learn a profitable lesson. Even though God may act as though He did not see (dissimulet) for a time, He still does not forget their iniquities. Wretched men foolishly imagine that the memory of these sins is blotted out, unless they are pursued by God’s immediate vengeance.