Exodus 25:21

ואל הארן תתן את העדות AND IN THE ARK THOU SHALT PUT THE TESTIMONY — I do not know why this is repeated for it has already been commanded, (v. 16) “and thou shalt put the Testimony in the ark”. One may say that it intends to tell us that whilst the ark is still by itself — i. e. without the cover — he should first put the Testimony into it, and only afterwards should he put the cover on it for the first time. Thus indeed do we find: that when he (Moses) erected the Tabernacle it is stated, (Exodus 40:20) “and he [took and] put the Testimony into the ark”, and afterwards it says, “and he put the cover upon the ark above it” (cf. Talmud Yerushalmi Shekalim 6:1).

וְנָתַתָּ֧ אֶת־הַכַּפֹּ֛רֶת עַל־הָאָרֹ֖ן מִלְמָ֑עְלָה וְאֶל־הָ֣אָרֹ֔ן תִּתֵּן֙ אֶת־הָ֣עֵדֻ֔ת אֲשֶׁ֥ר אֶתֵּ֖ן אֵלֶֽיךָ׃

And thou shalt put the covering above, upon the ark; and in the ark thou shalt put the Testimony that I shall give thee.