All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.

The noble Sharia encourages the remembrance of Allah at all times and in all situations, highlighting the immense virtue and merit of such remembrance. There are general virtues of remembrance, among the most important of which are attaining Allah's pleasure and forgiveness, and earning immense rewards. Allah says {what means}: " For Muslim men and women,- for believing men and women, for devout men and women, for true men and women, for men and women who are patient and constant, for men and women who humble themselves, for men and women who give in Charity, for men and women who fast (and deny themselves), for men and women who guard their chastity, and for men and women who engage much in God’s praise,- for them has God prepared forgiveness and great reward." {Al-Ahzab, 35}.

The Prophet Muhammad (peace be upon him) also said: “Would you like me to tell you the best and purest of your deeds in the estimation of your King, those which raise your degrees highest, those which are better for you than spending gold and silver, and are better for you than that you should meet your enemy and cut off one another's head?” On receiving a reply in the affirmative he said, “It is remembering God.” [Reported by At-Tirmidhi].

The learned men of the Muslim faith have unanimously agreed on the legitimacy (based on evidence from Sharia texts) and  permissibility of remembrance (dhikr) through narrations from the texts of Sharia while they have differed regarding the permissibility of other forms. One of the forms in question is the remembrance using the singular name "Allah," which we see as permissible for remembrance as follows:

His saying, exalted be He, {what means}: "And mention the name of your Lord [in prayer] morning and evening" [Surah Al-Insan: 25], and He also says, exalted be He, {what means}: "And mention the name of your Lord [in prayer] morning and evening, and during the night prostrate to Him and exalt Him a long [part of the] night" [Surah Al-Muzzammil: 8]. The most encompassing and renowned name for our Lord, exalted be He, is "Allah," to whom all the beautiful names and lofty attributes belong.

Furthermore, what is mentioned in His saying, exalted be He: "Say, 'Allah'" [Surah Al-An'am: 91], "They will surely say, 'Allah'" [Surah Al-Ankabut: 61], repeated in several verses, and His saying, exalted be He: "And to Allah belong the best names, so invoke Him by them" [Surah Al-A'raf: 180]. Supplication is remembrance, and remembrance is supplication, both of which encompass repeating His name alone.

His saying, exalted be He: "Say, 'Call upon Allah or call upon the Most Merciful. Whichever [name] you call - to Him belong the best names'" [Surah Al-Isra: 110], meaning, mention Him, exalted be He, by His name "Allah" or His name "Ar-Rahman" or any other of His beautiful names.

This is supported by the narration of Anas ibn Malik, may Allah be pleased with him, from the Prophet Muhammad, peace be upon him, who said: "The Hour (Resurrection) will not occur until 'Allah, Allah' is not said on earth..'" This was recorded by Imam Muslim in his Sahih in the Book of Faith, and by Imam Tirmidhi in the Book of Tribulations, who said it is a sound hadith, and by Imam Ahmad in his Musnad. Therefore, this is a singular name mentioned repeatedly in this hadith.

In another narration from Anas, may Allah be pleased with him, he said: The Messenger of Allah, peace be upon him, said: "The Hour will not be established upon anyone who says, 'Allah, Allah.'" This is recorded by Imam Muslim. The scholar Ali al-Qari, may Allah have mercy on him, commented on this hadith saying, "Meaning, if Allah is not mentioned, there is no wisdom in the survival of people. From this, it is understood that the world continues to exist due to the blessings of the knowledgeable scholars, the righteous worshippers, and the general believers. This is what At-Tabari, may Allah have mercy on him, meant by saying: 'The meaning of 'until it will be said [Allah, Allah]' is until the name of Allah is not mentioned and not worshipped'" [Mirqat al-Mafatih, Vol. 5/P. 226].

It is also reported in a hadith that the Messenger of Allah, peace be upon him, used to say in his supplication: "Allah, Allah, my Lord, I do not associate anything with Him." This is recorded by Al-Bukhari in his Al-Tarikh Al-Kabir and by Al-Tabarani. This indicates the Prophet's repetition of the singular name.

Regarding the story of Bilal's torture, may Allah be pleased with him, it is mentioned that they made him wander among the valleys of Mecca while he was saying, "One... One," and there is no report that the Prophet, peace be upon him, prohibited this.

Here are some quotes from scholars regarding the permissibility of remembering Allah by saying His name itself "Allah":

Ibn Abidin, may Allah have mercy on him, said: "Hisham narrated from Muhammad, from Abu Hanifa, that [Allah] is the greatest name of Allah, as stated by Al-Tahawi and many other scholars, even to the extent that they do not mention any name above it. This is mentioned in "Sharh al-Tahrir" by Ibn Amir Haj" [Radd al-Muhtar, Vol. 1/P. 5].

For more details, check the book [Fayd al-Qadir, Sharh al-Jami' al-Saghir, Vol. 2/P. 309] by Al-Munawi, may Allah have mercy on him, and [Al-Qasd al-Mujarrad fi Ma'rifat al-Ism al-Mufrad, p. 34] by Imam Ibn Ata' Allah al-Sakandari, may Allah have mercy on him. 

Regarding the objection raised by those who oppose mentioning the singular name of Allah, arguing that it does not form a complete meaningful sentence, it can be answered that the one who mentions this singular name is not addressing a creature, so it is not necessary for his speech to be complete and meaningful. This is because he is remembering Allah, Who is aware of him and his intentions.

The scholars have permitted mentioning and supplicating with the phrase "Ya Hu" (O He), and they have provided justification for its permissibility. They argued that grammarians use pronoun "He" to refer to the most recognized entities, meaning the entities recognized among creatures. Therefore, this term does not include the name of Allah The Almighty, because His name "Allah" is the most recognized entity absolutely, being the object of proof for the necessity of existence, characterized by attributes, free from imperfections, having no partner among creatures. "Hu" (He) refers to this unique entity. The pronoun is simply an indication that designates what is referred to, provided that nothing other than what is intended crosses the mind of the one making the supplication, as it returns to the one who initiated it. Al-Zajjaj, may Allah have mercy on him, said: "(There is no deity except Him) means there is no deity for every creature except Him, and it is interpreted in the context of initiation" [Ma'ani al-Quran wa I'rabuhu, Vol. 1/P. 336].

In addition, check the book {Mafatih al-Ghaib, Vol.1/Ps. 139-140} by Imam Al-Razi, may Allah be pleased with him.

In conclusion, there is no sin in remembering Allah using the term "Allah Allah" as it is a proper noun, indicating by connotation the necessary existence, described by the attributes, and free from defects. Similarly, using the term "Ya Hu" is permissible because it signifies the Oneness of Allah (Tawhid)-these practices are not considered innovations (bid'ah)- and the essential aspect of remembrance is consciousness of Allah The Almighty. And Allah The Almighty knows best.