'It's God's gift.' Islamic State fills
coffers with Iraqi government cash

Not God but Bashar.

"Crucial to its revenue is income derived from oil produced from large fields in eastern Syria, some of which it then sells on to its arch enemy, the Syrian government, according to an informed source on the ground and a senior US official in Washington.

“Much of the oil goes to the Assad regime,” said Danny Glaser, assistant secretary for terrorist financing at the US treasury. “There’s a business opportunity, there’s a need for both of them. The Assad regime needs the oil, Isis needs the cash and they’re willing to do business even as they’re fighting each other.” "

Ally rather than arch-enemy, co-ordinating attacks on Syrian rebels more than fighting each other.