By Him Who created male and female.This is similar to Allah's saying,وَخَلَقْنَـكُمْ أَزْوَجاًAnd We have created you in pairs. (78:8)It is also similar to saying,وَمِن كُلِّ شَىْءٍ خَلَقْنَا زَوْجَيْنِAnd of everything We have created pairs. (51:49)And just as these things that are being sworn by are opposites, likewise that which this swearing is about are opposing things.This is why Allah says,إِنَّ سَعْيَكُمْ لَشَتَّى