“Know thou assuredly that the essence of all the Prophets of God is one and the same. Their unity is absolute. God, the Creator, saith: There is no distinction whatsoever among the Bearers of My Message. They all have but one purpose; their secret is the same secret. To prefer one in honor to another, to exalt certain ones above the rest, is in no wise to be permitted. Every true Prophet hath regarded His Message as fundamentally the same as the Revelation of every other Prophet gone before Him. If any man, therefore, should fail to comprehend this truth, and should consequently indulge in vain and unseemly language, no one whose sight is keen and whose understanding is enlightened would ever allow such idle talk to cause him to waver in his belief.
The measure of the revelation of the Prophets of God in this world, however, must differ. Each and every one of them hath been the Bearer of a distinct Message, and hath been commissioned to reveal Himself through specific acts. It is for this reason that they appear to vary in their greatness. Their Revelation may be likened unto the light of the moon that sheddeth its radiance upon the earth. Though every time it appeareth, it revealeth a fresh measure of its brightness, yet its inherent splendor can never diminish, nor can its light suffer extinction.
It is clear and evident, therefore, that any apparent variation in the intensity of their light is not inherent in the light itself, but should rather be attributed to the varying receptivity of an ever-changing world. Every Prophet Whom the Almighty and Peerless Creator hath purposed to send to the peoples of the earth hath been entrusted with a Message, and charged to act in a manner that would best meet the requirements of the age in which He appeared. God’s purpose in sending His Prophets unto men is twofold. The first is to liberate the children of men from the darkness of ignorance, and guide them to the light of true understanding. The second is to ensure the peace and tranquillity of mankind, and provide all the means by which they can be established.”
Gleanings From the Writings of Bahá’u’lláh page 78 & 79