וַיְהִ֗י מִקֵּץ֙ אַרְבָּעִ֣ים י֔וֹם וְאַרְבָּעִ֖ים לָ֑יְלָה נָתַ֨ן יְהוָ֜ה אֵלַ֗י אֶת־שְׁנֵ֛י לֻחֹ֥ת הָאֲבָנִ֖ים לֻח֥וֹת הַבְּרִֽית׃
I stało się po upływie czterdziestu dni, i czterdziestu nocy, że dał mi Wiekuisty dwie tablice kamienne, tablice przymierza;
Chizkuni
ויהי מקץ ארבעים יום וארבעים לילה, “it was at the end of forty days and forty nights;” these forty nights had expired at dawn on the Friday of the seventeenth day in Sivan.
Da'at Zekenim
שני לוחות, “two Tablets;” they symbolised bride and groom, as well as the two respective groomsmen and bridesmaids, as well as heaven and earth, the written and oral law, the physical world and the spiritual world. Rabbi Chanina points out that the word luchot, is written defectively, both letters ו, being missing. This is to teach that each Tablet is considered as equally important as is its partner.
Ibn Ezra
at the mark either the beginning or the end of the forty days [cf. comment on Numbers 13: 25]. Scripture here reveals that on the very day when Moshe was given the tablets, the Golden Calf was made.