mystical intercourse between Baha'u'llah and Abdul Baha

This Will and Testament as Shoghi Effendi have said, is the child of the Covenant. He gives the analogy in his writings. He says that he here portrays Bahá’u’lláh as if Bahá’u’lláh... He says, as a mystical intercourse between the person of Bahá’u’lláh - I'm paraphrasing it for you - and ‘Abdu’l-Bahá as the mother and Bahá’u’lláh here acting as the father. As a result of this mystical intercourse between the person of Bahá’u’lláh and ‘Abdu’l-Bahá, a child was born and that is the Will and Testament.

-Adib Taherzadeh in his lecture "Speaking about the development of Bahá’í administration, tests, and George Townshend"

https://bahai.works/Transcript:Adib_Taherzadeh/Speaking_about_administration,_tests,_Townshend