Bahá’u’lláh married Asiyih Khanum in Tihrán in 1251 AH (1835) when He was over 18 years of age. Asiyih Khanum, later surnamed Navvab by Bahá’u’lláh, was a daughter of a nobleman, Mírzá Isma'il-i-Vazir. Her date of birth is not known. She was a most noble and faithful follower of Bahá’u’lláh who served her Lord until the end of her life in 1886. There were seven children of the marriage, four of whom died in childhood. The other three were 'Abbas, entitled the 'Most Great Branch', ‘Abdu’l-Bahá; Fatimih, entitled Bahiyyih Khanum, the Greatest Holy Leaf; and Mihdi, entitled 'the Purest Branch'.

Adib Taherzadeh, The Child of the Covenant, p. 22

In one of His Tablets Bahá’u’lláh bestows upon Navvab the unique distinction of being His perpetual consort in all the worlds of God. The three members of the family of Navvab occupy the highest rank in the Faith. ‘Abdu’l-Bahá is, of course, the Centre of the Covenant of Bahá’u’lláh, the Perfect Exemplar and the embodiment of all divine virtues. His sister, the Greatest Holy Leaf, is regarded as the noblest woman of this Dispensation and its outstanding heroine. Her life was laden with unbearable sufferings in the path of Bahá’u’lláh and dedicated to the service of His Cause. The third child of Navvab was her noble and long-suffering son, the Purest Branch. He was the one who, in the prime of youth, offered up his life in the path of his Lord when he fell through a skylight in the prison of 'Akká onto the floor below. In a prayer revealed after the martyrdom of the Purest Branch, Bahá’u’lláh makes the following statement, which Shoghi Effendi describes as astounding: I have, O my Lord, offered up that which Thou hast given Me, that Thy servants may be quickened, and all that dwell on earth be united. (Shoghi Effendi, God Passes By, p. 188)

Adib Taherzadeh, The Child of the Covenant, p. 23

Navvab, honoured by Bahá’u’lláh with the designation 'the Most Exalted Leaf', was the embodiment of true nobility. She was utterly detached from the things of the world and was faithful to the Cause of God. Her deep attachment to the Cause of Bahá’u’lláh was one of her great distinguishing features. She had a compassionate and loving nature, was patient, humble and utterly resigned to the will of Bahá’u’lláh. Navvab suffered a great deal at the hands of those in the family who later broke the Covenant. Her faith in Bahá’u’lláh, whom she knew as the Supreme Manifestation of God, was resolute and unshakable. She served her Lord with exemplary devotion and complete self-effacement. Her daughter, the Greatest Holy Leaf, has described her in these words: I wish you could have seen her as I first remember her, tall, slender, graceful, eyes of a dark blue -- a pearl, a flower amongst women. I have been told that even when very young, her wisdom and intelligence went remarkable. I always think of her in those earliest days of my memory as queenly in her dignity and loveliness, full of consideration for everybody, gentle, of a marvellous unselfishness, no action of hers ever failed to show the loving-kindness of her pure heart; her very presence seemed to make an atmosphere of love and happiness whenever she came, enfolding all comers in the fragrance of gentle courtesy.

Lady Blomfield, Chosen Highway, p. 39-40