Tafsiran Ulangan 27:8: Rashi, Ibn Ezra, Rashbam & Siftei Chakhamim

באר היטב EXPLAINING THEM WELL — i.e. in seventy languages (Sotah 32a; cf. Rashi on Deuteronomy 1:5).

thoroughly clarified i.e., the writing.

'וכתבת על האבנים את כל דברי וגו, for when they were now sworn at Mount Gerizim and Mount Eyval the Torah was present before them in written format, and they were sworn to keep its commandments.