Al-Haashir (the Gatherer) is one of the names of the Prophet (peace and blessings of Allaah be upon him); it is not one of the names of Allaah
This hadeeth – “I am the Gatherer at whose feet the people will gather” – is one upon which the two Shaykhs (al-Bukhaari and Muslim) are agreed. The hadeeth in full is as follows: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “I have several names. I am Muhammad and I am Ahmad and I am al-Maahi (the Eraser) by means of whom Allaah erases (yamhu) kufr, and I am al-Haashir (the Gatherer) at whose feet the people will gather, and I am al-‘Aaqib (the successor, i.e., the one who succeeds the other Prophets in bringing about good, or the Last Prophet).” Narrated by al-Bukhaari, 4896; Muslim, 2354.
With regard to the phrase “I am the Gatherer at whose feet the people will gather”, what this means is that they will be gathered after him, and he will be gathered before the people. This is in accordance with what he said in another hadeeth: “The people will be gathered at my heels.”
It is possible that what is referred to by feet (qadam) is time, i.e., my era when my mission starts, when the signs of the gathering begin to appear, referring to the fact that there will be no Prophet after him. This was suggested by al-Haafiz in al-Fath, 6/557.
Ibn al-Qayyim said in Zaad al-Ma’aad (1/94): It is as if he was sent to gather the people.
Secondly: Your saying that Allaah is also called al-haashir is not correct, because the names of Allaah are determined by the texts of the Qur’aan and Sunnah, and there is no room for human reasoning with regard to them. We must accept what has been narrated in the Qur’aan and Sunnah and not add anything or take anything away.
1 – Because human reason cannot encompass the names that Allaah deserves, so we must accept what the texts say, because Allaah says (interpretation of the meaning):
“And follow not (O man, i.e., say not, or do not, or witness not) that of which you have no knowledge. Verily, the hearing, and the sight, and the heart of each of those ones will be questioned (by Allaah)”
“Say (O Muhammad): (But) the things that my Lord has indeed forbidden are Al‑Fawaahish (great evil sins and every kind of unlawful sexual intercourse) whether committed openly or secretly, sins (of all kinds), unrighteous oppression, joining partners (in worship) with Allaah for which He has given no authority, and saying things about Allaah of which you have no knowledge”
2 – Because calling Him by a name by which He has not called Himself, or denying one of the names by which He has called Himself is a transgression against His rights. We must observe proper etiquette in this matter and limit ourselves to those names that have been mentioned in the texts.
3 – The attributes of Allaah are greater than His names, because each name refers only to one attribute. For example, one of His names is al-Samee’ (the All-Hearing). This name affirms that al-Samee’ is a name of Allaah and affirms that He possesses the attribute of hearing.
With regard to the actions that are attributed to Allaah, they do not include the names of Allaah, because they are connected to His actions, and His actions have no end (or limit). Among the actions that are attributed to Allaah are coming, taking, withholding and striking, as He says:
“And your Lord comes with the angels in rows”
“Do they then wait for anything other than that Allaah should come to them in the shadows of the clouds and the angels?”
“So Allaah seized (destroyed) them for their sins”
[Aal ‘Imraan 3:11]
“He withholds the heaven from falling on the earth except
by His Leave”
“Verily, (O Muhammad) the Seizure (punishment) of your Lord is severe and painful”
These things are attributed to Allaah in the way in which they are mentioned in the Qur’aan, but we do not call Him by them, so we do not say that among his names are “the Comer” or “the Seizer” or “the Withholder” etc, but we say about Him and attribute that (action) to Him.
See Risaalat Qawaa’id al-Mathlaa by Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him), 2/283, in Majmoo’ Fataawa wa Rasaa’il al-Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him).