The poetry of Ha’azinu hammers away at two ideas. Zachor, remembering, is the good word, remember Shabbat, remember what your enemies tried to do. Remember mistakes like Miriam’s. Forgetting is negative, destructive. It implies intent.
“Remember the days of old.” But “You have grown, fat and complacent and deserted God.”
“But you have forgotten the Rock that gave birth to you.”
“But in the end God will avenge His enemies and forgive His people.”
This relationship between God and his people runs right through the Bible, of love, unfaithfulness and rejection. The Book of Hosea where he is told to marry a harlot to know what unfaithfulness feels like, is the culmination of this trope. But it is repeated to this day. We seem unable to learn.