May 7

“And I will give power unto my two witnesses, and they shall prophesy a thousand two hundred and three-score days, clothed in sackcloth.” [Revelation. 11:3] These two witnesses are Muhammad the Messenger of God, and ‘Alí, son of Abú Tálib.

In the Qur’án it is said that God addressed Muhammad, the Messenger of God, saying: “We made You a Witness, a Herald of good news, and a Warner”—that is to say, We have established Thee as the witness, the giver of good tidings, and as One bringing the wrath of God. The meaning of “a witness” is one by whose testimony things may be verified. The commands of these two witnesses were to be performed for twelve hundred and sixty days, each day signifying a year. Now, Muhammad was the root, and ‘Alí the branch, like Moses and Joshua. It is said they “are clothed in sackcloth,” meaning that they, apparently, were to be clothed in old raiment, not in new raiment; in other words, in the beginning they would possess no splendor in the eyes of the people, nor would their Cause appear new; for Muhammad’s spiritual Law corresponds to that of Christ in the Gospel, and most of His laws relating to material things correspond to those of the Pentateuch. This is the meaning of the old raiment. 
(‘Abdu’l-Baha, table talks in Akka, authenticated by ‘Abdu’l-Baha; ‘Some Answered Questions’)