Two Words for a Hardened Heart, and a List Never Numbered

The plague narrative alternates between two different Hebrew idioms for Pharaoh's resistance, one in which Pharaoh's own heart is hardened or hardens itself, and one in which God is said to harden it, a variation source critics read as evidence of two originally separate strands of plague tradition later combined, generally associated with the Priestly and Yahwist sources respectively, though the exact division of individual verses between them remains debated. Traditional Jewish philosophy and commentary instead reads the alternation theologically, generally holding that Pharaoh hardened his own heart through the first several plagues before God's hardening took over as a form of judgement removing his freedom to repent, a sequence discussed at length by medieval Jewish philosophers including Maimonides.

The Torah itself never states in one place that there were exactly ten plagues; the number becomes fixed only through later tradition and liturgy, most visibly the Passover Haggadah's enumeration, while the poetic recollections of the plagues in Psalms 78 and 105 each list a different selection in a different order from the Exodus narrative and from each other, a divergence long noted by biblical scholars studying how the same national memory was retold across different biblical genres.