Maybe not the best translation, but at least you will have a hint about what they are singing:
Come on! Come on, brothers!
God has opened the door; the door to paradise!
And in my soul I hear the beautiful song of hope!
Go away, don't delay; leave the cowards and the scared!
Leave the world and sacrifice everything for the merciful religion of Allah!
Come on! Come on, brothers!
God has opened the door; the door to paradise!
And in my soul I hear the beautiful song of hope!
Come on, lions of the earth; sharpen your paws and teeth!
The infidels came to remember their memory at "al-Akhzab!"