This is a very weak hadeeth. The justification in the hadeeth is that Allah when he created the creation, lied down and crossed one leg over the other. That is why the Prophet salla Allahu alaihi wa sallam forbade us from doing so.

Ahmad reported from Abu an-Nadr that Abu S’aeed al Kudry was suffering from a sore leg,and his brother came in and saw him lying with one leg crossed over the other,so he hit him on the leg!Did not you know it is sore? He said: Of course i knew He said “What made you to do that?He said”Did you not hear that the prophet salla Allahu alahi wa sallam forbade us to do this?