Bahá'u'lláh recalled the endeavour and the achievement of His Son, ‘Abdu’l-Baha

In Baghdad We Ourselves would go and take a seat in the coffee-house to meet the people -- friends and acquaintances, strangers and inquirers alike. We brought those who were remote near to the Faith, and led many a soul into the fold of the Cause. Thus We served the Cause of God, gave victory to His Word and exalted His Name. The Most Great Branch undertook the same task and served in the same way, to a much greater degree, in Adrianople, and then to a far greater extent and with greater efficacy, in 'Akká. The same hardships and afflictions which were Ours in the early days befell Him. In Baghdad We were not prisoners, and the Cause of God had not obtained even a fraction of the fame which it has gained today. At that time the number of its opponents and adversaries and ill-wishers was far less than today. In the Land of Mystery [Adrianople] We used to meet with some and let them come into Our presence. But in the Most Great Prison We do not meet the people who are not within the fold of the Cause. We have closed the doors of social intercourse. It is the Master Who has taken every trouble upon Himself. For Our sake, in order that We may have ease and comfort, He faces the world and its peoples. For Us He has become a mighty stronghold, a mighty armour. At first He rented the Mansion of Mazra'ih. We were there for a while. Then he secured for Us this Mansion of Bahji. He has arisen with all His power to serve the Faith, and confirmation crowns His effort. This work so occupies His days and nights that He is perforce kept away from Bahji for weeks. We consort with the Friends and reveal His [God's] Word. He, the Master, is the target and bears all hardships. (Baha’u’llah, quoted by Haji Mirza Haydar-'Ali in his autobiography “The Delight of Hearts”; Balyuzi, “Abdu'l-Baha - The Centre of the Covenant”, p. 25)