Islamic traditions that pointed to 'Abdu'l-Baha!Haji Mirza Haydar-'Ali, whom we have come to know in these pages, has recorded another testimony by Baha'u'llah to the station and the powers of His Son. The Haji had composed a treatise, drawing upon those Islamic traditions which pointed to 'Abdu'l-Baha. This compilation and commentary he presented to Baha'u'llah. Applauding it, Baha'u'llah told him that his deductions and conclusions were absolutely right.
Ref. : 'Abdu'l-Baha - The Centre of the Covenant of Baha'u'llah by H. M. Balyuzi