Hazrat Imam Mahdi (as) bears the special characteristics and more from the previous prophets. He is the embodiment of their virtues and qualities. He carries their signs and is the inheritor of all that they stood for and what was revealed upon them. The following article mentions the similarity between Hazrat Saleh (as) and Imam Mahdi (as).
Occultation and doubts
Hazrat Saleh (as) went into occultation from his people. After that when he returned to them a majority of them denied him as mentioned in the book of Kamaluddin.
Imam Sadiq (as) said, “Hazrat Saleh (as) remained in occultation from his community for a period of time. The day he disappeared from them he was of middle age, wide belly, elegant body, thick beard, fair complexioned and medium height. When he returned to his people, they did not recognize him from his face. And he found them divided into three groups, A group had denied him and they were not prepared to retract their denial. Another group was of those who had doubts about him. The third group was firm in its faith.
So he addressed the group of doubters and said, ‘I am Hazrat Saleh (as).’ They denied and chided him and snubbed him saying, ‘May Allah become aloof from you, Hazrat Saleh (as) was indeed having a different appearance.’
The Imam says, Then Hazrat Saleh (as) went to the deniers and they paid no heed to his words and expressed a deep hatred for him.
After that he went to the third group which was a group of faithful believers and told them that he was Hazrat Saleh (as). They said, ‘Please tell us something through which we may not have any doubt about you. We have no doubt that Allah, the Mighty and the High, Who is the Creator can change the appearance of anyone He wants. We had been informed about it and we have researched and studied the signs and portents regarding the reappearance of the Qaem. And it would be correct when he brings the news from the heavens.
Hazrat Saleh (as) said, I am that same Saleh (as) who brought the she-camel by miracle. They said, You are right. It is the same point we argued on. But tell us what its sign was? An alternate day was reserved for this she-camel to drink from the stream and alternate for you. We have brought faith on Allah and also believed on whatever you have brought.
At that time Allah, the Mighty and the High said, “Do you know that Saleh (as) is sent by his Lord?” (Chapter 7 verse 75) And the believers and people of faith said, “Surely we are believers in what he has been sent with.” (Chapter 7 verse 75) And the arrogant ones – those who doubted him – said, “Surely we are deniers of what you believe in.” (Chapter 7 verse 76)
The narrator asked, Was there among them a scholar and who knew Hazrat Saleh (as)? Imam replied, The Almighty Allah is more equitable that He should leave the earth without a scholar that guides the people to Allah. This community passed seven days in this manner after the reappearance and advent of Hazrat Saleh (as) as they had no recognition of a leader or Imam for themselves. But in spite of this they has something from divine religion and they had remained firm on that. Their beliefs were same. And when Hazrat Saleh (as) reappeared they gathered around him. And there is no doubt that the similarity of Imam Mahdi (as) is like that of Hazrat Saleh (as).” (Kamaluddin volume 1 page 136)
(The above article was taken and adapted from the book Mikyalul Makarim Fee Fawaedid Dua Lil Qaem)