I fell down In a way of humiliation and supplication, on your behalf. Forty days The same forty that were mentioned Deuteronomy 9:18, as appears by comparing this with the account given in Exodus, where this history is more fully related, and where this is related to have been done twice only. See Exodus 32:10; Exodus 33:5.
Related Commentaries of Deuteronomy 9:25
Deuteronomy 9:25
25 Thus I fell down before the LORD forty days and forty nights, as I fell down at the first; because the LORD had said he would destroy you.