Is it permissible to swear by other than Allah, as in our saying: "Qasaman bin-nazilatil-mahiqat" (I swear by the descending, obliterating [calamities])? And should we refrain from reciting the national anthem if it is not permissible?

It is legislated that an oath must only be taken by Allah the Exalted, because an oath is an act of veneration, and veneration is due to none but Allah. Therefore, it is impermissible for a Muslim to swear by other than Allah, or to repeat a saying that involves swearing by other than Allah; due to the Prophet's (peace and blessings be upon him) saying: "Whoever takes an oath, let him swear by Allah or remain silent," and his saying: "Whoever swears by other than Allah has committed shirk (polytheism)."