Bahá'u'lláh sends Nabíl-i-A`zam to Cairo to enquire after Hájí Mírzá Haydar-`Alí. He is thrown into prison and befriends a Christian cellmate, Fáris Effendi, who soon becomes a Bahá'í. [BKG248, 265–6; EB268; GPB178]
See BKG265–8 for an account of Nabíl's arrest and imprisonment.
Fáris Effendi is probably the first Christian to become a Bahá'í. [RB3:10]