InvestigateTruth

This can be understood in a few ways, which I try to explain one of them. The rest can be understood from the Book of Iqan:

One is that, based on the Baha'i teachings, from Adam to Muhammad is one cycle in the history of human's progress. In this cycle there came a number of guidance from God who called themselves prophets and Messengers. Adam was the first, and Muhammad was the last of them, which ended the Adamic Cycle. The Adamic cycle lasted 6000 years (The first creation, in 6 days, each day 1000 years).
Now we are in a new Cycle (start of the new creation), which started by Baha'u'llah, and will last 500,000 years. In this new cycle of human's progress, which is called, "the Cycle of fulfillment" the guidance continues to come from God, but they will be called Manifestation of God.


“Are We wearied out with the first creation? Yet are they in doubt with regard to a new creation!” Qur’án 50:15

Baha'u'llah wrote in the Iqan about Menifestations:

"Nay, all else besides these Manifestations, live by the operation of their Will, and move and have their being through the outpourings of their grace. ... Nay, all in their holy presence fade into utter nothingness, and are a thing forgotten. Human tongue can never befittingly sing their praise, and human speech can never unfold their mystery."



Another way to understand this, is that Muhammad was the last messenger untill the Final Day of Judgment, the Last Day. But on the Day of Judgement, the humanity was to meet with God. Since it is impossible to see God, and actually meet Him, this was meant meeting with the Manifestation of God, who would Judge between the Truth and false:

"Arise [O Baha'u'llah], and proclaim unto the entire creation the tidings that He Who is the All-Merciful hath directed His steps towards the Ridván and entered it. Guide, then, the people unto the garden of delight which God hath made the Throne of His Paradise. We have chosen thee to be our most mighty Trumpet, whose blast is to signalize the resurrection of all mankind." Gleanings

"By Him Who is the Great Announcement! The All-Merciful is come invested with undoubted sovereignty. The Balance hath been appointed, and all them that dwell on earth have been gathered together. The Trumpet hath been blown, and lo, all eyes have stared up with terror, and the hearts of all who are in the heavens and on the earth have trembled, except them whom the breath of the verses of God hath quickened, and who have detached themselves from all things." Gleanings

"Speed out of your sepulchers. How long will ye sleep? The second blast hath been blown on the trumpet. On whom are ye gazing? This is your Lord, the God of Mercy." Baha'u'llah, Gleanings

(the first trumpet was blown by the Bab)

"Verily this is that Most Great Beauty, foretold in the Books of the Messengers, through Whom truth shall be distinguished from error and the wisdom of every command shall be tested. " Tablet of Ahmad