R. Eliezer says: The Holy One Blessed be He said to Moses: Moses, My children are in trouble. The sea is raging and the foe is pursuing and you stand and prolong your prayers? For R. Eliezer was wont to say: There is a time to prolong (prayer) and a time to shorten. (Numbers 12:13) "G–d, I pray You, heal her" — to shorten. (Devarim 9:18) "And I fell down before the L–rd (in prayer) as at first, forty days and forty nights" — to prolong.