Is it permissible to swear by other than Allah, for example (by the Prophet) or (by Shaykh So-and-So)?

The questioner : Also, from the questions of the listener, a man from Egypt residing in Riyadh, who asks: Is it permissible to swear by other than Allah, for example by the Prophet, or by Shaykh So-and-So?

The Shaykh : Yes. Swearing by other than Allah is not permissible, because the Prophet (peace and blessings be upon him) prohibited it and said: In fact, the Prophet (peace and blessings be upon him) classified it as shirk (associating partners with Allah), where he said: Therefore, it is not permissible to swear by the Prophet, nor by a wali (close friend of Allah), nor by an angel, nor by one's homeland, nor by one's nationality, nor by any created being. One only swears by Allah (Mighty and Majestic) and by His attributes (Glorified and Exalted is He). For example, one says, "By Allah, the Most High, the Magnificent," or "By Allah, the Most Merciful, the Most Compassionate," or "By the Lord of the Ka'bah," or one says, "By the majesty of Allah" or "the power of Allah," or similar attributes. It is permissible to swear by these.
And despite this, one should not swear excessively, due to the saying of Allah the Exalted: One of the interpretations of this is: Do not swear excessively by Allah, especially if the swearing involves lying, for the matter is serious in that case. If the lie in the oath involves consuming the wealth of others without right, and it is known that there is no right in lying, then the Prophet (peace and blessings be upon him) said: This is the oath that plunges its owner into sin and then into the Fire, may Allah protect us from that.
It should be known that if a person swears by Allah and couples his oath with the will of Allah, then there is no expiation (kaffarah) upon him if he breaks the oath. For example, if he says, "By Allah, I will certainly do such-and-such, if Allah wills," or "By Allah, if Allah wills, I will certainly do such-and-such," then if he does not do it, he owes nothing. This is because the Prophet (peace and blessings be upon him) said: Therefore, a person should couple his oath with the will of Allah whenever he swears, for he benefits in two ways. The first benefit is the facilitation of the matter and the attainment of the intended goal. The second benefit is that the expiation does not become obligatory upon him if he breaks the oath.
The evidence for the first matter, which is the facilitation of affairs when a person couples his oath with the will of Allah, is what is established in the authentic collections from the Prophet (peace and blessings be upon him) that Sulayman (peace be upon him) said, "By Allah, I will certainly go around tonight with ninety women, each of whom will give birth to a boy who will fight in the cause of Allah." The angel said to him, "Say, 'If Allah wills.'" He did not say, "If Allah wills," due to the strength of his resolve (peace and blessings be upon him). So he went around with ninety women that night, but only one of them gave birth to a split human being, to make it clear to Allah (Mighty and Majestic) for him and for others that the matter is in His hand (Glorified and Exalted is He), and that it is not permissible for anyone to swear by Allah (Mighty and Majestic) in a way that implies certainty. The Prophet (peace and blessings be upon him) said in this hadith:
As for the second matter, which is that if he says "if Allah wills" and then breaks the oath, there is no expiation upon him, that is what I mentioned earlier from his saying (peace and blessings be upon him): Yes.

The questioner : May Allah bless you.