In the Hadith:

The Holy Prophet (sallal laahu alaihi wasallam) said, “whosoever has touched the name Muhammad with his hands, then kissed his hand with his lips and rubbed it on his eyes, then he will see Allah Ta’ala just as righteous ones see and my intercession will be close to him even though he is a sinner.’’ (An Nawafi ul Atri’aa)

In Jannat, when Hazrat Adam (alaihis salaam) desired to meet the Holy Prophet (sallal laahu alaihi wasallam), then Allah Ta’ala sent Wahi (revelation) to him, “From your generation, he will become apparent in the later years.” Then Hazrat Adam (alaihis salaam) desired from Allah Ta’ala to meet the Holy Prophet (sallal laahu alaihi wasallam). Allah Ta’ala showed him the Noor of the Holy Prophet (sallal laahu alaihi wasallam) on the Shahadat finger of his right hand. The Noor recite the Tasbeeh of Allah Ta’ala. It is for this reason that this finger is known as the kalmia finger. Allah Ta’ala showed the beauty of Holy Prophet (sallal laahu alaihi wasallam) on the thumbnails of Hazrat Adam (alaihis salaam) like a mirror. Then, Hazrat Adam (alaihis salaam) kissed his both the thumbnails and turned them over his eyes.

Thus, this Sunnah of Hazrat Adam (alaihis salaam) became consistent in his descendant. When Hazrat Jibraeel Ameen (alaihis salaam) informed Rasoolullah (sallal laahu alaihi wasallam) of this he said, “that person, who when hearing my name in Azaan, kisses his thumbnails and turns it over his eyes, he shall never go blind.” (Tafseer Roohul Bayaan).

Once the Holy Prophet (sallal laahu alaihi wasallam) entered the Masjid and sat down near the pillar. Hazrat Abu Bakr Siddique (radi Allahu anhu) was seated beside him. Hazrat Bilal (radi Allahu anhu) then stood up and commenced with Azaan. When he said: “ Ash hadu Ana Muhammadur Rasoolullah”, Hazrat Abu Bakr Siddique (radi Allahu anhu) placed his both the thumbnails on to his eyes and said “Qurratu Aini Bika Ya Rasoolullah” ( Ya Rasoolullah! You are the coolness of my eyes). When Hazrat Bilal completed Azaan, the Holy Prophet (sallal laahu alaihi wasallam) said, “O Abu Bakr! Whosoever does like you have done, Almighty Allah will forgive his all sins.” (Tafseer Roohul Bayaan).

Sayyiduna Imam Hasan (radi Allahu anhu) said Whosoever hears the Mu’azzin say’ “ Ash hadu Ana Muhammadur Rasoolullah” and says “Marhaba bi Habibi” and “Quratu Aini Muhammad Bin Abdullah” and then kisses his both the thumbs and keeps it on his eyes, then he will never become blind and his eyes will never be sore.” (Maqaaside Husna).

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In fiqh, the discussion of taqbil al-unbulatayn wa mash al-’aynayn is usually found at the end of Bab Adhan. Certain gestures performed during the adhan, and specifically the ‘amal of kissing the thumbs and wiping the eye, are something known to Shafi’is, and there can be no objection whatsoever by our jurists (and any jurists for that matter) to those wishing to perform this ‘amal: as far as we are concerned, it is classified under the category of the Fada’il al-A’mal [I’anat, 1:243; al-Jurdani, Fath al-‘Allam, 2:140-1].

Among its legal bases [‘ilal] is that it is a Sunna of the first Khalifa of the Messenger of Allah (may Allah’s blessings and peace be upon him!) [i.e., an Athar of the first Khalifa], and it is also based on a number of Hadiths, of which the most well known is the Hadith of Abu Bakr (may Allah be well pleased with him!).