This morning a quote telling of the person of Baha'u'llah came to mind and I thought I would offer it to
@Milton Platt but as you have replied to him, I will offer it to you as well.
As suggested, a Messenger does not come to prove they can do miracles as they hold the power of all life, they can do as they please, except they choose to to God's Will.
So the passage that came to mind is from a person that met Baha'u'llah, Edward G. Browne;
"The face of him on whom I gazed I can never forget, though I cannot describe it. Those piercing eyes seemed to read one’s very soul; power and authority sat on that ample brow; while the deep lines on the forehead and face implied an age which the jet-black hair and beard flowing down in indistinguishable luxuriance almost to the waist seemed to belie. No need to ask in whose presence I stood, as I bowed myself before one who is the object of a devotion and love which kings might envy and emperors sigh for in vain!"
This is the one of the greatest and lasting proofs of a Manifestation of God, that no earthly king can inspire and is why people at times, confuse the Messenger from God, for God. This is why they still have followers, even after thousands of years.
Yet none of them came to be a King of this world and in their actions they prove what they came for, and that is to win our hearts so that we can find a unity of purpose in serving each other within the laws given by God. When we achieve this it becomes the outer realisation of the Lords Prayer, Thy Kingdom come, Thy Will be done on earth as it is in Heaven.
Regards Tony