וָֽאֶתְנַפַּ֞ל לִפְנֵ֣י יְהוָ֗ה אֵ֣ת אַרְבָּעִ֥ים הַיּ֛וֹם וְאֶת־אַרְבָּעִ֥ים הַלַּ֖יְלָה אֲשֶׁ֣ר הִתְנַפָּ֑לְתִּי כִּֽי־אָמַ֥ר יְהוָ֖ה לְהַשְׁמִ֥יד אֶתְכֶֽם׃
Also fiel ich vor dem HERRN in den vierzig Tagen und vierzig Nächten nieder, in denen ich hinfiel; weil der Herr gesagt hatte, er würde dich vernichten.
Zohar
To pray quickly (is like the prayer of Moshe), "Heal her now, K-l, I pray You" (Bemidbar 12:13), (he addressed) the point of Yud. (Where) one should pray at length, as in 'to fall down' : "And I fell down (Heb. va'etnapal) before Hashem, as at the first..." (Devarim 9:18) (this is the letter Peh) "forty days and forty nights" (40 plus 40 equals 80, the letter Peh). Everything (is in the two) Mem's. (The) Yud as a point in the middle, which forms the word Mayim (Eng. 'water'). From the aspect of Chesed, one should pray at length.