ghamdi ko qadyani b pasand karte hein sirf is liye ke wo unki merzi ki baat karta hai ke Hazrat essa ka intekaal hogaya hai aur imam mehdi nahi ana..
I searched following Sahih Sitta Books for Immam Mahdi:
1. Sahih Bukhari
2. Sahih Muslim
3.
Malik's Muwatta
I could find only one hadeeth, again yes only one hadeeth which has the name of "Imam Mahdi":
Abu Nadra reported:" We were in the company of Jabir b. 'Abdulldh that he said it may happen that the people of Iraq may not send their qafiz and dirhams (their measures of food stuff and their money). We said: Who would be respolisible for it? He said: The non_Arabs would prevt them. He again said: There is the possibility that the people of Syria may not send their dinar and mudd. We said: Who would be responsible for it? He said This prevention would be made by the Romans. He (Jabir b. Abdullab) kept quiet for a while and then reported Allah', s Messengdt (may peas be upon him) having said There would be a caliph in the last (period) of my Ummah who would freely give handfuls of wealth to thd people wiothout counting it. I said to Abu Nadra and Abu al-'Ala: DO you mean 'Umarb. 'Abd al-Aziz? They said: No (he would be Imam Mahdi). (Sahih Muslim, Book #041, Hadith #6961) Source
The point to be noted that sentence "he would be Imam mahdi" is written within bracket, meaning that this sentence was not part of the original text and that it was added later.
Then I searched
Sunan Abudawud, I found following hadeeths:
Narrated Umm Salamah, Ummul Mu'minin: The Prophet (peace_be_upon_him) said: The Mahdi will be of my family, of the descendants of Fatimah. Abdullah ibn Ja'far said: I heard AbulMalih praising Ali ibn Nufayl and describing his good qualities.
(Sunan Abudawud, Book #36, Hadith #4271)
Narrated AbuSa'id al-Khudri: The Prophet (peace_be_upon_him) said: The Mahdi will be of my stock, and will have a broad forehead a prominent nose. He will fill the earth will equity and justice as it was filled with oppression and tyranny, and he will rule for seven years. (Sunan Abudawud, Book #36, Hadith #4272) Source
Now the question is that why an important issue such as appearance of imam Mahdi could not find place in Quraan and many books of authentic Hadeeths?
Islam came and destroyed the concept of hereditary (موروثی) rank. The Quran declares that people are created inherently equal and differ only based on their Taqwa (piety):
يَا أَيُّهَا النَّاسُ إِنَّا خَلَقْنَاكُم مِّن ذَكَرٍ وَأُنثَىٰ وَجَعَلْنَاكُمْ شُعُوبًا وَقَبَائِلَ لِتَعَارَفُوا ۚ إِنَّ أَكْرَمَكُمْ عِندَ اللَّهِ أَتْقَاكُمْ ۚ إِنَّ اللَّهَ عَلِيمٌ خَبِيرٌ (Quran, 49:13)
Yusuf Ali 13:
O mankind! We created you from a single (pair) of a male and a female, and made you into nations and tribes, that ye may know each other (not that ye may despise (each other). Verily the most honoured of you in the sight of Allah is (he who is) the most righteous of you. And Allah has full knowledge and is well acquainted (with all things).
ا ے لوگو ہم نے تمہیں ایک ہی مرد اور عورت سے پیدا کیا ہے اور تمہارے خاندان اور قومیں جو بنائی ہیں تاکہ تمہیں آپس میں پہچان ہو بے شک زیادہ عزت والا تم میں سے الله کے نزدیک وہ ہے جو تم میں سے زیادہ پرہیزگار ہے بے شک الله سب کچھ جاننے والا خبردار ہے
• The Hadiths
The Prophet (صلّى الله عليه وآله وسلّم) declared that people were born inherently equal “except by piety and good action (Taqwa). Indeed the best among you is the one with the best character (Taqwa). Listen to me. Did I convey this to you properly?…Each one of you who is here must convey this to everyone not present.” (Excerpt from the Prophet’s Last Sermon as in Baihiqi)
The Prophet (صلّى الله عليه وآله وسلّم) said:“There are indeed people who boast of their dead ancestors; but in the sight of Allah they are more contemptible than the black beetle that rolls a piece of dung with its nose. Behold, Allah has removed from you the arrogance of the Time of Jahiliyyah (Ignorance) with its boast of ancestral glories. Man is but an Allah-fearing believer or an unfortunate sinner. All people are the children of Adam, and Adam was created out of dust.” [At-Tirmidhi and Abu Dawud]
The Prophet (صلّى الله عليه وآله وسلّم) said further: “Undoubtedly Allah has removed from you the pride of arrogance of the age of Jahiliyah (ignorance) and the glorification of ancestors. Now people are of two kinds. Either believers who are aware or transgressors who do wrong. You are all the children of Adam and Adam was made of clay… If they do not give this up (i.e. pride in ancestors) Allah will consider them lower than the lowly worm which pushes itself through Khara (dung).” [Abu Dawud and Tirmidhi]
'A'isha, the wife of Allah's Apostle (may peace be upon him), reported that the Quraish were concerned about the woman who had committed theft during the lifetime of Allah's Apostle (may peace be upon him), in the expedition of Victory (of Mecca). They said: Who would speak to Allah's Messenger (may peace be upon him) about her? They (again) said: Who can dare do this but Usama b Zaid, the loved one of Allah's Messenger (may peace be upon him)? She was brought to Allah's Messenger (may peace be upon him) and Usama b. Zaid spoke about her to him (interceded on her behalf). The colour of the face of Allah's Messenger (may peace be upon him) changed, and he said: Do you intercede in one of the prescribed punishments of Allah? He (Usama) said: 'Messenger of Allah, seek forgiveness for me. When it was dusk. Allah's Messenger (may peace be upon him) stood up and gave an address. He (first) glorified Allah as He deserves, and then said: Now to our topic. This (injustice) destroyed those before you that when any one of (high) rank committed theft among them, they spared him, and when any weak one among them committed theft, they inflicted the prescribed punishment upon him. By Him in Whose Hand is my life, even if Fatima daughter of Muhammad were to commit theft, I would have cutoff her hand. He (the Holy Prophet) then commanded about that woman who had committed theft, and her hand was cut off. 'A'isha (further) said: Hers was a good respentance, and she later on married and used to come to me after that, and I conveyed her needs (and problems) to Allah's Messenger (may peace be upon him). [Sahih Muslim, Book# 017, Hadeeth# 4188]
After reading above verses of Quraan and hadith it would be accusation on Prophet Muhammad (صلی اللہ علیہ وآلہ وسلم) if some insists that Prophet Muhammad (صلی اللہ علیہ وآلہ وسلم) praised and exalted his progeny (آل اولاد) and lineage (حسب نسب). After all, how could the Prophet Muhammad (صلی اللہ علیہ وآلہ وسلم) praise and exalt (مرتبہ) his progeny (آل اولاد) and lineage (حسب نسب) whilst forbidding anyone else from glorifying their lineage? It is mostly shia Aqaeed where they emphasis on linage.