Deuteronomy — Chapter 9

And I fell down before the Lord as before, forty days and forty nights, eating no bread, and drinking no water, for all your sins. Moses's triple fast in Sinai (or double, as Cajetan holds) shows the power of priestly intercession. Moses prayed for the people who had worshipped the calf, and God relented. This is the pattern of all priestly intercession for sinners.