I have already referred.

In a Tablet addressed to a Baha'i in Mazindaran, in which He unfolds the
meaning of a misinterpreted statement attributed to Him regarding the rise
of the Sun of Truth in this century, He sets forth, briefly but
conclusively, what should remain for all time our true conception of the
relationship between the two Manifestations associated with the Baha'i
Dispensation. "In making such a statement," He explains, "I had in mind no
one else except the Bab and Baha'u'llah, the character of whose
Revelations it had been my purpose to elucidate. The Revelation of the Bab
may be likened to the sun, its station corresponding to the first sign of
the Zodiac--the sign Aries--which the sun enters at the Vernal Equinox. The
station of Baha'u'llah's Revelation, on the other hand, is represented by
the sign Leo, the sun's mid-summer and highest station. By this is meant
that this holy Dispensation is illumined with the light of the Sun of
Truth shining from its most exalted station, and in the plenitude of its
resplendency, its heat and glory."

"The Bab, the Exalted One," 'Abdu'l-Baha more specifically affirms in
another Tablet, "is the Morn of Truth, the splendor of Whose light shineth
throughout all regions. He is also the Harbinger of the Most Great Light,
the Abha Luminary. The Blessed Beauty is the One promised by the sacred
books of the past, the revelation of the Source of light that shone upon
Mount Sinai, Whose fire glowed in the midst of the Burning Bush. We are,
one and all, servants of their threshold, and stand each as a lowly keeper
at their door." "Every proof and prophecy," is His still more emphatic
warning, "every manner of evidence, whether based on reason or on the text
of the scriptures and traditions, are to be regarded as centered in the
persons of Baha'u'llah and the Bab. In them is to be found their complete
fulfillment."

And finally, in His Will and Testament, the repository of His last wishes
and parting instructions, He in the following passage, specifically
designed to set forth the guiding principles of Baha'i belief, sets the
seal of His testimony on the Bab's dual and exalted station: "The
foundation of the belief of the people of Baha (may my life be offered up
for them) is this: His holiness the exalted One (the Bab) is the
Manifestation of the unity and oneness of God and the Forerunner of the
Ancient Beauty (Baha'u'llah). His holiness, the Abha Beauty (Baha'u'llah)
(may