The Kitáb-i-Aqdas - The Most Holy Book
Index term: Twin Houses, under Holy Places and Historical Sites
k32.
The Lord hath ordained that those of you who are able shall make pilgrimage to the sacred House, and from this He hath exempted women as a mercy on His part. He, of a truth, is the All-Bountiful, the Most Generous.
k133.
Raise up and exalt the two Houses in the Twin Hallowed Spots, and the other sites wherein the throne of your Lord, the All-Merciful, hath been established. Thus commandeth you the Lord of every understanding heart.
n54.
The Lord hath ordained that those of you who are able shall make pilgrimage to the sacred House
Two sacred Houses are covered by this ordinance, the House of the Báb in Shíráz and the House of Bahá'u'lláh in Baghdád. Bahá'u'lláh has specified that pilgrimage to either of these two Houses fulfils the requirement of this passage (Q&A 25, 29). In two separate Tablets, known as Súriy-i-Hajj (Q&A 10), Bahá'u'lláh has prescribed specific rites for each of these pilgrimages. In this sense, the performance of a pilgrimage is more than simply visiting these two Houses.
After the passing of Bahá'u'lláh, 'Abdu'l-Bahá designated the Shrine of Bahá'u'lláh at Bahjí as a place of pilgrimage. In a Tablet, He indicates that the "Most Holy Shrine, the Blessed House in Baghdád and the venerated House of the Báb in Shíráz" are "consecrated to pilgrimage", and that it is "obligatory" to visit these places "if one can afford it and is able to do so, and if no obstacle stands in one's way". No rites have been prescribed for pilgrimage to the Most Holy Shrine.
n68.
Shave not your heads
In some religious traditions it is considered desirable to shave one's head. The shaving of the head is forbidden by Bahá'u'lláh, and He makes it clear that the provision contained in His Súriy-i-Hajj requiring pilgrims to the Holy House in Shíráz to shave their heads has been superseded through this verse of the Kitáb-i-Aqdas (Q&A 10).
n154.
Raise up and exalt the two Houses in the Twin Hallowed Spots, and the other sites wherein the throne of your Lord . . . hath been established.
Bahá'u'lláh identifies the "two Houses" as His House in Baghdád, designated by Him as the "Most Great House", and the House of the Báb in Shíráz, both of which have been ordained by Him as sites of pilgrimage. (See Q&A 29, 32 and note 54.)
Shoghi Effendi explained that "the other sites wherein the throne of your Lord . . . hath been established" refers to those places where the Person of the Manifestation of God has resided. Bahá'u'lláh states that "the people of the areas where these are situated may choose to preserve either each house" wherein He resided, "or one of them" (Q&A 32). Bahá'í institutions have identified, documented, and where possible, acquired and restored a number of the historical sites associated with the Twin Manifestations.
q32.
 
Question: Concerning the restoration and preservation of the two Houses in the Twin Spots, and the other sites wherein the throne hath been established.
Answer: By the two Houses is intended the Most Great House and the House of the Primal Point. As for other sites, the people of the areas where these are situated may choose to preserve either each house wherein the throne hath been established, or one of them.