There is an old conundrum that goes something like this: If all the Prophets of God were to meet in this room, and there was only one chair, Who would sit in it? Followers of each One, of course, believe that theirs should take the chair, and are often prepared to fight about it.
The answer, of course, is that no One of Them would exalt Himself above the others, because they are each speaking with the same Voice, sharing the Word of God. Each one has referred to the Others--Those Who came before, and Those to come in the future.
The three wise men whom Christian tradition credits with travelling a long distance in search of the Anointed One were probably Zoroastrian priests following their religious prophecies. Christ told His listeners that if they had known Moses, they would know Him. Moses acknowledged Abraham. Muhammad wrote more about both Moses and Christ in the Qur'an than occurs in the Bible. And so Bahá'u'lláh, Prophet-Founder of the Bahá'í Faith, makes it clear to His followers that they must accept and respect each of Those Who have come before, as well as prepare to receive the next One.
The concept is called progressive revelation. As mankind has evolved, as civilization develops, God provided Teachers to guide--and admonish where the guidance has been ignored or misunderstood. Even as children have many teachers as they go through school, God has sent His Manifestations throughout the ages. Just as elementary school teachers may know much more than they teach but tailor their presentations to the needs and development of their students, so do these wonderful Messengers of God instruct mankind.
Christ is quoted as saying that He could not answer all the Apostles' questions because, “I have yet many things to say unto you, but ye cannot bear them now. Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come. He shall glorify me: for he shall receive of mine, and shall shew it unto you. All things that the Father hath are mine: therefore said I, that he shall take of mine, and shall shew it unto you. A little while, and ye shall not see me: and again, a little while, and ye shall see me, because I go to the Father. King James Bible, John 16:12-16
Bahá'ís believe that truth is gradually revealed to mankind, in every age and time, throughout history. The Word is available to us, to be found no matter which Prophet, no matter by which name the Creator is known. Competition among them exists only in the minds of men, not in the Word. Apparent differences can be explained by the social teachings fitted to the age in which they were revealed to apply the Word in a way that people of that time could understand them.
Bahá'u'lláh has explained the process of progressive revelation this way: "Know of a certainty that in every Dispensation the light of Divine Revelation hath been vouchsafed to men in direct proportion to their spiritual capacity." - Synopsis and Codification of the Kitáb-i-Aqdas, p. 5)
Bahá'ís believe this is the day foretold by prophesy in all the religions of God. This is the day when mankind's maturity is in sight, when it will be possible to build "God's Kingdom on Earth as it is in Heaven."
I believe it, but I do not require this belief of anyone else. Each of us must find his/her own way. Bahá'u'lláh tells his followers, "A man's faith is conditioned by no one but himself…" - from Great Themes of Life