"With reference to ... the Dispensation of Baha'u'llah, he wishes me to
explain that although 'Abdu'l-Baha's station is not that of a
Manifestation of God, nevertheless supplications may be addressed to Him.
It is essential, however, that every believer should realize that while
doing so he is directing his thoughts toward the Master as an intermediary
between him and the Manifestation, and not as the Source of Divine
Revelation and Spiritual Guidance. Provided this distinction is clearly
established, there can be no harm or objection in addressing prayers to
'Abdu'l-Baha."