I read this Bible passage with my daughter Matilda last night:
Ex. 32:11 But Moses implored the LORD his God and said, “O LORD, why does your wrath burn hot against your people, whom you have brought out of the land of Egypt with great power and with a mighty hand? 12 Why should the Egyptians say, ‘With evil intent did he bring them out, to kill them in the mountains and to consume them from the face of the earth’? Turn from your burning anger and relent from this disaster against your people. 13 Remember Abraham, Isaac, and Israel, your servants, to whom you swore by your own self, and said to them, ‘I will multiply your offspring as the stars of heaven, and all this land that I have promised I will give to your offspring, and they shall inherit it forever.’ ” 14 And the LORD relented from the disaster that he had spoken of bringing on his people.
The idea that God would 'relent' (which essentially means to 'repent', just the way a sinner would repent of sin) is extraordinary, especially when the apparent cause of that repentance is the prayer of Moses.
The basis of the repentance cannot be the reminder of God's promises, since these could be fulfilled just as adequately through Moses (even if he is a descendant of Levi—see Ex 2:1). That is in fact what God had planned to do ("Now therefore let me alone, that my wrath may burn hot against them and I may consume them, in order that I may make a great nation of you."—Ex 32:10). So we have to conclude that the basis of God's repentance is his concern for his reputation amongst the Egyptians (See also Ex 7:5; 17; Ex 8:10, 22; 14:4, 18 and compare Ex 8:19 and Ex 9:16).
Did our Lord have this passage in mind in Gethsemane?
Mk 14:36 And he said, “Abba, Father, all things are possible for you. Remove this cup from me. Yet not what I will, but what you will.”
Both the example of Moses and the example of Jesus should drive us to prayer in the face of impending disaster. If the answer is 'yes', disaster has been averted. If the answer is 'no', then we know that the disaster is the LORD's will, and that in the very depths of despair he is with us still, as he was with his Son on the cross.