Surnamed Áqáy-i-Kalím, a younger brother of Bahá'u‘lláh who remained devoted and faithful to Bahá'u'lláh and served Him to the end of his life. After the Martyrdom of the Báb, Mírzá Músá, at Bahá'u'lláh's instructions, hid the casket containing the remains of the Báb in the Shrine of Imám-Zádih Ḥasan in Ṭihrán. Mírzá Músá accompanied Bahá'u'lláh into exile and often served as His deputy in meeting with government officials and religious leaders, until ‘Abdu'l-Bahá took on this function. Shoghi Effendi designated him one of the Nineteen Apostles of Bahá'u'lláh. Mírzá Músá died in ‘Akká in 1887.