What is the ruling on saying "We have pledged allegiance to you, O Messenger of Allah" when discussing the pledges of allegiance, and saying "I sacrifice my life for you" to the Messenger or his Companions?

If the person who says this was a contemporary of the Prophet, peace and blessings be upon him, or his companions, then there is no blame on him. This was common among the Salaf and the Prophet, peace and blessings be upon him, approved of it. Redemption (tafdeeyah) is permissible for the Prophet and for others, such as the Companions or scholars. It has been reported that the Companions said to the Prophet, peace and blessings be upon him, "May my father and mother be sacrificed for you." Ibn Abbas did not rebuke Saeed ibn Jubair for saying, "May Allah make me your sacrifice." The people of knowledge have unanimously agreed that phrases of redemption such as "by my father and mother" and "may Allah make me your sacrifice" and "my soul be a sacrifice for your soul" are not disliked.