What is the ruling on saying "may He cover your sister's sins (yastur 'ala ukhtik)," "amanah (I entrust you by God)," and "karamah li an-nabi (out of reverence for the Prophet)" with the intention of pleading during speech?

The supplicant's saying, "May He conceal your sister," is a prayer, and there is no harm in it. However, regarding the saying "Amana" (trust) or "Amana and the dignity of the Prophet," if the intention behind it is an oath, then it is not permissible. This is due to the prohibition of swearing by other than Allah, whether by "Amana" or by the Prophet and his attributes, for all of these are created beings. Whoever's tongue is accustomed to this, let him accustom himself to abandoning it.