Exodus 25:16

Καὶ ἐμβαλεῖς εἰς τὴν κιβωτὸν τὰ μαρτύρια, ἃ ἂν δῶ σοι.

And you shall put into the ark the testimonies whichever I shall give to you.

ונתת אל־הארן את העדת אשׁר אתן אליך׃

*   Exodus 25:16 = Exodus 25:15 in other LXX editions
*   testimonies OR witnesses