By what proof can ye establish the truth of Muhammad, Whom we sent aforetime?

If He Who hath come unto you with clear verses be not the True One from God, even as ye proclaim this day from your seats of worldly honour, then by what proof can ye establish the truth of Muhammad, Whom we sent aforetime? Be fair in your judgement, O concourse of ill-wishers!

- Days of Remembrance (Selections from the Writings of Bahá’u’lláh for Bahá’í Holy Days)

http://www.bahai.org/library/authoritative-texts/bahaullah/days-remembrance/days-remembrance.docx?fa27a24c