Old Testament readings use the Septuagint , the Scripture the apostles quoted. Masoretic numbering shown for reference.Learn why
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Deuteronomy 31:21

It will happen, when many evils and troubles have come on them, that this song will testify before them as a witness; for it will not be forgotten out of the mouths of their descendants; for I know their ways and what they are doing today, before I have brought them into the land which I promised them.”

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