What is the ruling on saying "What does Allah have to do with it?" unintentionally, and is it considered disbelief (kufr), and is repentance obligatory if it is considered disbelief?

The phrase "fate willed it" is not devoid of ill manners towards Allah, but its utterer does not commit disbelief merely by saying it unless he intends mockery. Such phrases must be avoided out of reverence for Allah.