Between Fir`awn and the Sorcerers

His threats against them resulted only in an increase in their faith and submission to Allah, for the veil of disbelief had been lifted from their hearts and the truth became clear to them because they knew something that their people did not: that what Musa had done could not have been done by any human being unless Allah helped him, making it proof and an evidence of the truth of what he had brought from his Lord. Then Fir`awn said to them:

ءَامَنتُمْ لَهُ قَبْلَ أَنْ ءَاذَنَ لَكُمْ

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)