Old Testament readings use the Septuagint , the Scripture the apostles quoted. Masoretic numbering shown for reference.Learn why
LXX2012

Psalms 77:51

and struck every firstborn in the land of Egypt; the first fruits of their labors in the tents of Cham.

Parallel Translations

LXXView canonical →
and smote every first-born in the land of Egypt; the first-fruits of their labours in the tents of Cham.
Brenton's Septuagint Translation