Exodus 17:14-16

14Then the Lord said to Moses, ‘Write down what happened here in a book. Then people will remember it. Read it aloud for Joshua to hear. Say that I will completely destroy all the Amalekites. Nobody in the whole world will remember them any more.’

15Then Moses used big stones to build an altar. He called it ‘The Lord is my flag in war’.

16Moses said, ‘Take hold of the Lord's flag! The Lord will always continue to fight against the Amalekites.’