Siyyid Mustafa Rumi belonged to a noble family from Baghdad and had come to Madras to help his aged father in his business. Rumi was proficient in a number of languages including Arabic, Persian, Turkish, Gujarati, Bengali, Urdu and English. He became a Baha'i through the travel teacher, Jamal Effendi. He eventually settled in Rangoon, Burma, where he married into a prosperous Indo-Burman family of traders and joined his brothers-in-law in their business activities. The communities of Rangoon and Mandalay continued to grow slowly, Baha’u’llah sending the Baha'is there numerous Tablets through Rumi.

At the end of the 19th century the Baha'is of Burma made a beautiful marble sarcophagus to hold the remains of the Báb, Mustafa Rumi being one of three believers who helped pay for it. In 1899 Rumi, together with a few others, carried the sarcophagus to the Holy Land as a gift to 'Abdu'l-Baha, who welcomed them graciously. Another ten years would pass, however, before the Master was at last able, on Naw-Ruz 1909, to transfer the sarcophagus to the mausoleum on Mount Carmel, where the wooden casket containing the Báb’s remains was laid within it and the sarcophagusm interred in the Shrine.

As well as establishing the Baha’i communities of Rangoon and Mandalay, Rumi was also responsible for raising up the Baha'i community of Daidanaw, a village in the township of Kungyangoon. How this came about is an interesting story. It so happened that the headman of Daidanaw was embroiled in some legal case and he was in trouble. In the court of Rangoon when his bail application was admitted there was no one to stand surety for him because he was a stranger to the place. One of the Baha’is of Rangoon, ‘Abdu’l-Karim by name, happened to be in the court. He at once offered himself and another friend as sureties for the headman. This impressed the headman and his companions and they inquired of ‘Abdu’l-Karim to which Faith he belonged and when told of Baha’u’llah and His Great Message they evinced a great desire to hear it in detail. They were brought to Siyyid Mustafa who convinced them about the truth of the new Revelation. The headman and his party went back to their village and related their unique experience to the people. The elders of the village held a consultation and decided to invite Siyyid Mustafa to their village to teach them the new Faith of God. Siyyid Mustafa did it in his own convincing manner and the whole village of some 800 people embraced the Cause.

Desiring to help these new Baha'is, Rumi then obtained financial aid from the Rangoon believers and started a school in the village. In later years the Guardian strongly encouraged the Daidanaw community to maintain its school, sending 30 pounds through the care of Mustafa Rumi for its upkeep.
Siyyid Mustafa had a very sweet temper. He was an erudite scholar and knew the religious books of the Jews, the Christians, the Muslims and the Buddhists. He had a talent for bringing out their teachings in the light of the Baha’i Message in his own sweet way and in such a convincing manner that a beginner became enamoured and convinced. He might not, for worldly considerations, join the Baha’i Fold; but he knew for certainty in his heart of hearts, that no other Faith could redeem the world at the present time of the ills that had beset it.

Throughout his life Siyyid Mustafa served the Cause of humanity by showing the people the true path of felicity and salvation as taught by Baha’u’llah and many were the souls that found the elixir of life at his hands. Siyyid Mustafa had a unique capacity that most teachers lack. He was a great administrator. He would not only teach his beginners but would lead them to form themselves into a group and thus lay the foundation of a Spiritual Assembly, the first unit in the New World Order of Baha’u’llah. Power to teach and power to organize are two chief capacities which make a perfect Baha’i teacher and Siyyid Mustafa possessed both in abundance.
In the early 1930s Rumi was elected to the National Spiritual Assembly of India and Burma and served on it for several years. In later years he made his home in Daidanaw. During the Second World War many of the Baha'is of Rangoon and Mandalay took refuge in the village. It was a time of intense nationalistic fervor and people of foreign backgrounds were in particular danger. The Baha'is asked Rumi to escape from the village as he was in great risk of his life but he refused, referring to his advanced age and his determination not to leave the place he had chosen to serve.

On 13 March 1945 the village was attacked by a mob of three thousand people who surrounded it in order to purge it from all foreign influence. The Baha’i school, the Haziratu’l-Quds and many Baha'i homes were burned to the ground and property was looted. Most tragically, however, eleven Baha'is were killed in the attack, among them Siyyid Mustafa Rumi. The mob burned his home, beheaded him and chopped his body to pieces. Later the Baha'is gathered his body and buried him in front of the Baha’i centre. On 14 July 1945 the Guardian sent a cable to the Baha'is of India and Burma elevating Rumi to the rank of Hand of the Cause:
"11.11.1946 Greatly deplore tribulations afflicting dearly beloved Burmese friends profoundly moved circumstances attending assassination heroic apostle Baha’u’llah Sayed Mustafa and associates. Admire unquenchable spirit animating long suffering brethren Rangoon Mandalay Daidanow assure them admiration gratitude strong attachment fervent prayers revival activities. Soon transmitting one thousand pounds my contribution relief rebuilding institutions promotion teaching activities. Urge National Assembly immediate concentrated continual attention promote vital interests Burmese community—RABBANI"

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