Parashas Eikev · Passuk 10:2
I will inscribe on the tablets the commandments that were on the first tablets that you smashed, and you shall deposit them in the ark.”
Torah Temimah points to Menachot 99a.
TT lemma: ושמתם בארון (unit 2 of 2).
English: Rav Yosef taught: “Which you broke, and you shall place them in the ark” — this teaches that the tablets and the fragments of the tablets both rest in the ark.
Custom (broken tablets in the ark; respect for one who forgot Torah)
Broken tablets remain sacred in the ark; likewise one must not disgrace a scholar who lost his learning under duress.