From the traditional Islamic perspective, what is the significance of Muhammad uttering these words?
If thou art sailing upon the sea of God’s Names, which are reflected in all things, know thou that He is exalted and sanctified from being known through His creatures, or being described by His servants. Everything thou beholdest hath been called into being through the operation of His Will. How can such a created thing, therefore, be indicative of His essential oneness? God’s existence in itself testifieth to His Own oneness, while every created thing, by its very nature, beareth evidence that it hath been fashioned by God. Such is the proof of consummate wisdom in the estimation of those who sail the ocean of divine Truth.
If, however, thou art sailing upon the sea of creation, know thou that the First Remembrance, which is the Primal Will of God, may be likened unto the sun. God hath created Him through the potency of His might, and He hath, from the beginning that hath no beginning, caused Him to be manifested in every Dispensation through the compelling power of His behest, and God will, to the end that knoweth no end, continue to manifest Him according to the good-pleasure of His invincible Purpose.
And know thou that He indeed resembleth the sun. Were the risings of the sun to continue till the end that hath no end, yet there hath not been nor ever will be more than one sun; and were its settings to endure for evermore, still there hath not been nor ever will be more than one sun. It is this Primal Will which appeareth resplendent in every Prophet and speaketh forth in every revealed Book. It knoweth no beginning, inasmuch as the First deriveth its firstness from It; and knoweth no end, for the Last oweth its lastness unto It.
In the time of the First Manifestation the Primal Will appeared in Adam; in the day of Noah It became known in Noah; in the day of Abraham in Him; and so in the day of Moses; the day of Jesus; the day of Muḥammad, the Apostle of God; the day of the ‘Point of the Bayán’; the day of Him Whom God shall make manifest; and the day of the One Who will appear after Him Whom God shall make manifest. Hence the inner meaning of the words uttered by the Apostle of God, ‘I am all the Prophets’, inasmuch as what shineth resplendent in each one of Them hath been and will ever remain the one and the same sun.
Every discerning observer will recognize that in the Dispensation of the Qur’án both the Book and the Cause of Jesus were confirmed. As to the matter of names, Muḥammad, Himself, declared: “I am Jesus.” He recognized the truth of the signs, prophecies, and words of Jesus, and testified that they were all of God. In this sense, neither the person of Jesus nor His writings hath differed from that of Muḥammad and of His holy Book, inasmuch as both have championed the Cause of God, uttered His praise, and revealed His commandments. Thus it is that Jesus, Himself, declared: “I go away and come again unto you.” Consider the sun. Were it to say now, “I am the sun of yesterday,” it would speak the truth. And should it, bearing the sequence of time in mind, claim to be other than that sun, it still would speak the truth. In like manner, if it be said that all the days are but one and the same, it is correct and true. And if it be said, with respect to their particular names and designations, that they differ, that again is true. For though they are the same, yet one doth recognize in each a separate designation, a specific attribute, a particular character. Conceive accordingly the distinction, variation, and unity characteristic of the various Manifestations of holiness, that thou mayest comprehend the allusions made by the creator of all names and attributes to the mysteries of distinction and unity, and discover the answer to thy question as to why that everlasting Beauty should have, at sundry times, called Himself by different names and titles.
Where exactly did Muhammad ever say that?
Source please
Say ye: "We believe in Allah, and the revelation given to us, and to Abraham, Ismail, Isaac, Jacob, and the Tribes, and that given to Moses and Jesus, and that given to (all) prophets from their Lord: We make no difference between one and another of them: And we submit to Allah (in Islam)." - Qur'an 2:136
Thanks, let us leave it at that.
For an elaborate explanation of this click on the link below to understand the Baha'i concept of the Oneness of the Prophets.
Oneness of the Prophets
Yes, I was wanting to discuss Baha'u'llah and the the Báb's interpretation of the Koran.
Here is a quote from the Báb.
Baha'u'llah said:
I am wondering what Muslims are thinking of their interpretation. How much does it differ from their beliefs, and where can we find similarities?