When Ali Kuli Khan served the Cause in the United States, it happened that he frequently met with representatives of Iran in that country. In some of those situations, he had to take instant decisions of diplomatic character. In such situations, although he did his best, he felt that his limited wisdom restricted him from taking the best possible decisions. He therefore, wished he had a prayer he could recite to be guided in such situations. He had this question in His mind and thought of asking the Master about it.

When the Master arrived to Washington, Ali Kuli Khan met Him at the station. Ali Kuli Khan had this question in his heart and about halfway back from the station, the Master suddenly told a story to Ali Kuli Khan.

`Abdu’l-Bahá told of the time in Bagdad when Bahá’u’lláh had retired to the mountains. His family did not know where He had gone and were extremely worried. `Abdu’l-Bahá was a boy at that time and the absence of His Father was very difficult. One night, `Abdu’l-Bahá recited and supplicated with all his heart saying “Ya Allah el Mustaghas! Ya Allah el Mustaghas!” all night. In the morning after, at the break of dawn, `Abdu’l-Bahá received a message which he understood to be about the return of Bahá’u’lláh.

Ali Kuli Khan understood that the invocation of “Ya Allah el Mustaghas!” would be the prayer to utter in moments of need.

It seems that `Abdu’l-Bahá used this powerful prayer at different occasions. Mirzieh Gail recounts the following (Arches of the Years, page 312).

Shoghi Effendi also had the burden of the believers’ personal griefs. Florence once asked him for a very powerful prayer, and he answered, ‘What could be better than Yá Allahu’l-Mustaghath?’ … It was her understanding that this was the prayer repeated over and over by the Master, as He paced His garden when the Turkish ship was coming to take Him away.

The Universal House of Justice clarifies that the phrase “Yá Allahu’l-Mustaghath”, … is an invocation revealed by the Bab. He prescribed it for recitation by His followers in times of trouble and difficulty. Shoghi Effendi has translated the word “Mustaghath” as “He who is invoked for help”. (Universal House of Justice, 25 Nov 1999)

In the same letter, The Universal House of Justice clarifies that “In the Writings of the Bab, “Mustaghath” refers to Bahá’u’lláh, and “the time of ‘Mustaghath‘” refers to the time of Bahá’u’lláh’s Dispensation. … Mustaghath literally means “He Who is invoked. It denotes the cycle of every Divine Manifestation, referred to in the writings of the Báb and Bahá’u’lláh.” (Universal House of Justice, 25 Nov 1999)

It seems that the One being invoked for help is Bahá’u’lláh. Perhaps the following explanation of `Abdu’l-Bahá about the phrase “He is God”, can explain why Bahá’u’lláh is invoked.

Regarding the phrase ‘HE IS GOD!’ written above the Tablets. By this Word is intended that no one hath any access to the Invisible Essence. The way is barred and the road is impassable. In this world all men must turn their faces toward ‘Him-whom-God-shall-Manifest.’ He is the Dawning-place of Divinity and the Manifestation of Deity. He is the Ultimate Goal, the Adored One of all and the Worshipped One of all. Otherwise, whatever flashes through the mind is not that Essence of essences and Reality of realities; nay, rather it is pure imagination woven by man—consequently, it returns finally to the realm of suppositions and conjectures.” (Star of the West, Vol 4, issue 18, page 304)

The Universal House of Justice also clarifies that the number of times this phrase is to be repeated is up to the individual.

With regard to the number of times these words are to be repeated, the repetition of this invocation is not definitely fixed, and there is a great deal of flexibility concerning the repetition of this and other prayers. While the invocation is prescribed in the Writings of the Báb to be repeated 2098 times during occasions of great need, ‘Abdu’l-Bahá in one Tablet states that this verse is to be repeated 95 times and, in another Tablet, 81 times. Letters from the Guardian concerning this invocation, as well as other prayers, indicate that repetition is a matter of individual choice. In a postscript added in his own handwriting to a letter to an individual he stated: “There is no objection to saying “Yá Ilaha‘l-Mustaghath” any time you like and as often as you like.” (Universal House of Justice, 25 Nov 1999)

And finally, as to the correct transliteration, we have the following guidance.

This phrase can be correctly transliterated in two ways, as set out below: (elaha’l … ) “Yá Ilaha‘l-Mustaghath”, which has been translated as “O Lord of the time of ‘Mustaghath’ “[or] “Yá Allahu’l-Mustaghath”, which has been translated as “O Thou God Who art invoked” (Universal House of Justice, 25 Nov 1999)