Abû Hurayrah relates that the Prophet (peace be upon him) said: “Use my name when naming yourselves but do not use my kunyah as a kunyah for yourselves.”

It is an authentic hadîth related by al-Bukhârî and Muslim, among others.

The meaning of this hadîth:

A kunyah is an epithet for a person that at least superficially indicates paternity or maternity. It starts with either Abû (father) for a man or Umm (mother) for a woman followed by some other name. It is used as a respectful mode of address instead of calling someone by his or her given name. The kunyah of Prophet Muhammad (peace be upon him) was Abû al-Qâsim.

The Prophet (peace be upon him) had a son named al-Qâsim who died in his early childhood. The word ‘ qâsim ' literally means “one who divides or apportions”.

This hadîth has a story behind it. It is related in Sahîh Muslim from Anas b. Mâlik that in the graveyard of Madinah known as al-Baqî`, a man called out to another man by the kunyah Abû al-Qâsim. Because of this, Allah's Messenger (peace be upon him) turned around and looked at him. The man said: “O Messenger of Allah! I did not mean you. I was calling so-and-so.”

Allah's Messenger (peace be upon him) said: “Use my name when naming yourselves but do not use my kunyah as a kunyah for yourselves.” [ Sahîh Muslim ]

This statement is related to us by Jâbir in another context. A child was born to a man and he named that child Muhammad. His people said to him: “We shall not let you give him the name of Allah's Messenger (peace be upon him).”

So he set off carrying his son on his back and took him to the Prophet (peace be upon him) and said: “O Messenger of Allah! A son was born to me and I named him Muhammad, but my people said to me that they would not let me give him the name of Allah's Messenger (peace be upon him).”

Allah's Messenger (peace be upon him) said: “Use my name when naming yourselves but do not use my kunyah as a kunyah for yourselves, for indeed it is but I who am the “ qâsim ” who judges between you.” [ Sahîh Muslim ]

Its legal implications:

Scholars disagree as to the lawfulness of using the kunyah “Abû al-Qâsim” for someone. There are three opinions on the matter.

The first opinion is that it is categorically prohibited for anyone besides the Prophet (peace be upon him) to have this kunyah . According to this opinion, it makes no difference whether the person being referred to as Abû al-Qâsim has the name Muhammad or some other name. This is the view of the Shâfi`î and Zâhirî schools of law. They cite the hadîth mentioned above as evidence to support their opinion.

The second opinion is that it is perfectly permissible to use the kunyah Abû al-Qâsim. The prohibition was only in effect during the Prophet's lifetime. Al-Qâdî `Iyâd asserts that this is the opinion of the majority of scholars and jurists throughout the ages. The evidence used to support this opinion is as follows:

1. The story related in Sahîh Muslim that took place in the graveyard of Madinah gives a clear indication of why using this kunyah was prohibited. A ruling that has a particular reason for it ceases to take effect when the reason for it is no longer present.

2. It is related that `Alî b. Abî Tâlib asked the Prophet (peace be upon him): “O Messenger of Allah! If a child is born to me after you pass away, may I give him your name and refer to him by your kunyah ?”

The Prophet (peace be upon him) answered: “Yes, you may.” [ al-Adab al-Mufrid , Sunan Abî Dâwûd and Sunan al-Tirmidhî . It has been authenticated by al-Hâkim. Ibn Hajar declared its chain of transmission to be strong.]

In this hadîth, the Prophet (peace be upon him) gave `Alî his express permission to name his child Muhammad and to give him the kunyah of Abû al-Qâsim.

3. There is ample evidence that the Companions understood the prohibition to apply only during the lifetime of the Prophet (peace be upon him). There were Companions who gave their children the name Muhammad and referred to them by the kunyah Abû al-Qâsim. This was done by Abû Talhah. Also Abû Bakr, Sa`d, Ja`far b. Abî Tâlib, `Abd al-Rahmân b.`Awf, Hâtib b. Abî Balta`ah, and Ash`ath b. Qays all had sons named Muhammad and all of those sons were referred to by the kunyah Abû al-Qâsim.

The third opinion that has been expressed on this matter is that it is impermissible for a person named Muhammad to go by the kunyah of Abû al-Qâsim but permissible for others to do so. This opinion was preferred by al-Râfi`î, though it was declared a spurious opinion by al-Nawawî.

There is a hadîth that supports this view. It is reported that the Prophet (peace be upon him) said: “Whoever is called by my name should not go by my kunyah , and whoever carries my kunyah should not be given my name.” [ Sunan Abî Dâwûd and Musnad Ahmad ]

The second and third opinions that permit the use of Abû al-Qâsim are more correct than the first that forbids it categorically, since there is ample evidence that the prohibition mentioned in the hadîth is not of an absolute nature. The first opinion, however, is the safer one to follow. And Allah knows best.