Asalaamu alaykum, dear shaykh and brother in Islam. I have a question about the following hadith: Abdullaah, the freed slave of Asmaa' (the daughter of Abu Bakr), the maternal uncle of the son of 'Ata, reported:
"Asmaa' sent me to 'Abdullaah ibn 'Umar, saying, 'The news has reached me that you prohibit the use of three things: striped robes, saddle cloth made of red silk, and fasting in the holy month of Rajab.' 'Abdullah said to me, 'As for what you say about fasting in the month of Rajab, how about one who observes continuous fasting? And as for what you say about the striped garment, I heard Umar ibn Al-Khattaab say that he had heard from Allaah's Messenger (may peace be upon him), 'He who wears silk garment has no share for him (in the Hereafter),' and I am afraid it may not be that striped garment; and so far as the red saddle cloth is concerned, that is the saddle cloth of Abdullaah, and it is red.' I went back to Asmaa' and informed her. Thereupon, she said, 'Here is the cloak of Allaah's Messenger (may peace be upon him),' and she brought out to me that cloak made of Persian cloth with a hem of brocade and its sleeves bordered with brocade and said, 'This is Allaah's Messenger's cloak, it was with 'A'isha until she died, and when she died, I got possession of it. Allaah's Messenger, sallallaahu alayhi wa sallam, used to wear that, and we used it for the sick and sought cure thereby.'"
I am aware that this hadith proves that the prophet had some knowledge of the unseen of which Allaah, The Exalted, informed him. Some sects of Islam also claim that this hadith is also proof of the Prophet's intercession as his cloak was used to cure the sick as the hadith also states. How valid is this claim of theirs, and does this hadith also prove that the prophet, sallallaahu alayhi wa sallam, interceded in curing the sick? Please shed some light on this. Thank you, and may Allaah reward you.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger. 

The hadeeth that you mentioned is an authentic hadeeth that was narrated by Muslim, Ahmad and others. It clarifies that it is permissible to seek cure from the clothes worn by the Prophet because of the blessings that they have. This corresponds to other authentic ahaadeeth regarding seeking blessings with the effects of the Prophet such as his sweat and his hair. For more benefit, please refer to fataawa 25217 and 88236.

However, this is a way of seeking blessings and not a way of seeking intercession. The scholars do not have any difference of opinion on the permissibility of seeking this blessing, but this is peculiar to the Prophet as his Companions did not seek blessings with the effects of any other person than him .

The Fiqh Encyclopedia reads:

“The scholars agreed on the permissibility of seeking blessings with the Prophet and his relics, and the scholars of biography, virtues and Hadeeth reported a lot of information that shows that the Companions sought blessings in various forms from the Prophet and his relics. Ibn Rajab said: 'Seeking blessings with the relics (of the Prophet ) is something that the Companions used to do with the Prophet but they did not do so with each other, and the Taabi’is (the generation that followed that of the Companions) did not do so with the Companions despite the great status of the latter. This is evidence that this cannot be done except with the Prophet such as seeking blessings in the water that he used to perform wudhoo' (ablution) with, and with his other relics.”

However, this hadeeth has nothing to do with the Unseen; rather, Allaah informed the Prophet about many matters of the unseen, and the Prophet informed us about them, some of them have happened and some have not yet taken place. For more benefit, please refer to fatwa only knew the unseen that Allaah informed him about">91400.

Allaah knows best.