What is the ruling on one who says, "If I do such and such, then it is a curse against Allah," or "then it is a similitude of Allah Almighty with something that does not befit Him," or "then may Allah be cursed" – Allah forbid – and then intends to do this thing?

Swearing by a word of disbelief (kufr) is forbidden. If the one swearing intends disbelief by it, he commits an act of disbelief immediately. If he does not intend disbelief by it, he does not commit an act of disbelief. As for the ruling on expiation for swearing by a word of disbelief, there is a difference of opinion among scholars, and the majority holds that it is not obligatory. Therefore, whoever has done this must repent to Allah. He is not obligated to avoid what he swore to abandon, nor is he obligated to offer expiation according to most scholars.