﴿ فَأَلْقَوْا۟ حِبَالَهُمْ وَعِصِيَّهُمْ وَقَالُوا۟ بِعِزَّةِ فِرْعَوْنَ إِنَّا لَنَحْنُ ٱلْغَٰلِبُونَ ﴾

“Thereupon they threw their [magic ropes and their staffs, and said: “By Pharaoh’s might, behold, it is we indeed who have prevailed!””

بِعِزَّةِ فِرْ‌عَوْنَ (By the majesty of the Pharaoh - 26:44). This was an expression of pledge from the magicians, which was in vogue in the olden times. It is unfortunate that similar oaths have now become common among the Muslims as well, which are even more evil and vile, for instance, 'by the king,' 'by the head of yours,' 'by the beard of yours,' 'by the grave of your father' etc. It is not permitted to make an oath of this nature under the Islamic law (because swearing in the name of someone other than Allah is a sin). Rather, it will not be wrong to say that swearing a true oath in this way is as much sinful as swearing a false oath in the name of Allah. (Ruh)