Islam has encouraged the custom of greetings among the members of Society because it leads to love and friendship.  This is supported by the Prophet’s peace and blessings of Allah be upon him, saying:

“You will never enter Paradise until you become believers, and you will not become believers until you love each other. Shall I guide you to something that makes you love each other? Spread greetings with peace among you.” (Muslim)

The Qasidah Burdah or "poem of the shawl" was written by Imam Saalih Sharafuddeen Abu Abdullah Muhammad ibn al-Hasan al-Busairi Rahimahullah. He had become paralysed and his doctors gave up all hope of recovery. In this state of complete helplessness and despair he composed this poem in praise of Rasulullah Sallallahu Alayhi Wasallam. Using this as his sole means of seeking a cure from the divine court of Allah Ta'aala he isolated himself in a quiet place on the night of Jummuah. With total sincerity and concentration he began reciting this poem, crying and begging Allah through the intercession of Nabi Sallallahu Alaihi Wasallam. While reciting it he was overcome by sleep. He was blessed with the vision of Rasulullah Sallallahu Alayhi Wasallam. He mentioned to Rasulullah Sallallahu Alayhi Wasallam his illness. Rasulullah Sallallahu Alyahi Wasallam passed his blessed hand over Imaam Busairi's face and placed a shawl over him. Through the barakah (blessings) of Rasulullah Sallallahu Alayhi Wasallam, Allah Ta'aala granted him complete cure from his paralysis.
 
In the morning when due to some necessity, he went to the market, a pious dervish greeted him and requested him to recite the Qasidah which he had composed in praise of Rasulullah Sallallahu Alayhi Wasallam. The Imaam replied that he had composed many poems in praise of Rasulullah Sallallahu Alayhi Wasallam. The dervish replied: "I require the one which begins with 'Amin tazak-kuri jeeraani.' "
 
Hearing this the Imaam became wonder struck and said: "I take an oath that no one knows about this poem. Please tell me from who did you hear about it?"
 
The dervish replied: "I take an oath by Allah that I heard it from you last night when in a dream you had recited it to Rasulullah Sallallahu Alayhi Wasallam. Rasulullah Sallallahu Alayhi Wasallam was very pleased with it, he threw a shawl over you and because of this blessing Allah Ta'aala granted you complete cure from your ailment".
 
When the Imaam gave this poem to the dervish his secret became known to all the people and its barakah (blessings) too became general for all. The news also reached the ruler Baha-ud-deen who called for him. He had the poem written down and would listen to it standing with respect. Once Saadud-deen Faarooqi, the viceroy of Baha-ud-deen, became blind. In a dream he saw a person who told him to take 'the shawl' from Baha-ud-deen and place it on his eyes. In the morning he told Baha-ud-deen about this dream. Baha-ud-deen said that he did not have any of blessed relics of Nabi Sallallahu Alaihi Wasallam in his possession. Later he realized that 'the shawl' could refer to the Qasidah Burdah. The poem was brought and and Saadud-deen placed it on his eyes. Through its barakah Allah Ta'aala granted him complete cure and restored his eyesight. From then on the poem became known as the Qasidah Burdah, 'poem of the shawl.'  (See Al Waafi Bil Wafayaat)