Prophecies if they are true, they will come to be true.
Prophecies of the coming of many prophets predicting their coming and describing some events had taken place in the past; the reason for the prophecy is to let people anticipate the coming of that particular prophet.
This was true about Moses: there were such prophecies about his coming, when the Children of Israel anticipated the coming of Moses as their savior.
Jesus also. John Baptist before him.
And there were many prophecies before the coming of Jesus, among people.
There were three persons the people at that time were anticipating: the Christ, the Prophet [Mohammed] and Elia of the Last Days.
So when John Baptist started to admonish people, some people scholars came and asked him:
We see you speak with authority: who are you? Are you the Christ [the Messieh]? He said: I am not him.
They said are you the Prophet [Mohammed]? He said: I am not him.
They said are you Elia [of the Last Days (the Mahdi whose part of his name is also Ali which means Elia in Hebrew)? He said: I am not him.
They said: What are you then? He said: I am a voice in the wilderness to prepare the way before the Christ.
These prophecies about the Last Day and their explanation:
The Disagreement of the
Refer also to the Gospel of John 1: 19-23