January 14. On this date in 1953, Shoghi Effendi wrote "Bahá'u'lláh married the first and second wives while He was still in Tihrán, and the third wife while He was in Baghdád. At that time, the Laws of the "Aqdas" had not been revealed, and secondly, He was following the Laws of the previous Dispensation and the customs of the people of His own land."

January 14. On this date in 1953, Shoghi Effendi wrote "Bahá'u'lláh married the first and second wives while He was still in Tihrán, and the third wife while He was in Baghdád. At that time, the Laws of the "Aqdas" had not been revealed, and secondly, He was following the Laws of the previous Dispensation and the customs of the people of His own land."

...Bahá'u'lláh married the first and second wives while He was still in Tihrán, and the third wife while He was in Baghdád. At that time, the Laws of the "Aqdas" had not been revealed, and secondly, He was following the Laws of the previous Dispensation and the customs of the people of His own land.
(14 January 1953 to an individual believer)

Bahá'u'lláh was 18 years old when he married his first wife, Ásíyih, who was fifteen years old.  Bahá'u'lláh became a Bábí in 1844, at the age of 27, and Ásíyih became a Bábí that same year at the age of 23.

Bahá'u'lláh's second wife, Fatimih, was twenty years old when she married Bahá'u'lláh in 1849.

In 1862, Bahá'u'lláh married his third wife, Gawhar, who was actually a servant of his first wife Ásíyih. The age at marriage of Gawhar is unknown.

At the time Bahá'u'lláh married Fatimih in 1849 and Gawhar in 1862, he was a Bábí and subject to the laws of the Bayan. At the time of his marriage to his third wife, Gawhar, he continued to have children with his second wife, Fatimih. While there is no English translation of the Persian Bayan, there is a French translation which addresses this topic...

Bayan Persan - UNITE 7 - PORTE 15
Dans ceci qu'il est obligatoire pour un chacun de prendre une femme afin que reste de lui quelqu'un qui unifie Dieu, son Seigneur. Certes il faut s'efforcer d'avoir un enfant (ou de se marier). Si se manifeste d'un homme ou d'une femme l'impuissance à avoir un enfant, il est licite pour l'époux non impuissant (quel qu'il soit) de se remarier à nouveau après en avoir obtenu l'autorisation de l'autre partie, mais non sans sa permission. Et ce afin que se manifeste de cet époux ou de cette épouse un enfant.