"His are the Keys of the Treasures of the Heavens and the Earth: He enlarges and restricts the sustenance to whom He will: for He knows full well all things." (42:12)
It is reported that Uthman ibn Affan, may Allah be pleased with him, requested further information about Allah's injunction of the Keys of the Treasures of the Heavens and the Earth (mentioned several times in the Qur'an). The Prophet (s.a.w.s.) said to him: "You have inquired of me something which nobody has ever asked me before. They Keys of the Treasures of the Heavens and the Earth are as follows":
The Prophet (s.a.w.s) continued: "O Uthman! Whoever recites it one hundred times every day will be rewarded ten graces. First, all his sins will be forgiven. Second, his suffering from hellfire will be written off. Third, two angels are appointed to guard him day and night from sufferings and diseases. Fourth, he is granted a treasure of blessings. Fifth, he will reap as much blessing as someone who would have set free one hundred slaves from the offspring of prophet Ishmael (a.s.). Sixth, he would be rewarded of blessings as if he had read the entire Qur'an, the Psalms, the Torah, and the Injeel. Seventh, a house will be constructed for him in the Heaven. Eight, he will be married to a pious Heavenly maiden. Ninth, he will be honored with a crown of honor. Tenth, his recommendation (for forgiveness) of seventy of his relatives will be accepted.
"O Uthman! If you were strong enough you would not miss this remembrance on any day. You will be one of the successful ones and you will surpass everybody before you and after you." 
One of the great contemporary Sufis, Hazrat Abu Anees Barkat Ali of Dar-ul-Ehsan, Pakistan, has achieved a unique position among the men of piety by reciting this sacred formula. He has erected a large signpost at the entranceway of his spiritual sanctuary, upon which the words of this invaluable formula are inscribed. His own life bears ample testament to the efficacy of these words, as he has personally adopted more than ten thousand Hindus of the lowest caste and provided them with a complete training and education in life. Moreover, he maintains a clinic that provides medical care and that has restored the sight of more than three thousand persons so far, without charge of any kind. He has written more than three hundred books on Islam and Sufism, all of which have been distributed free of charge (the jacket of one reads: "These books are written for ourselves and you to read, but not for sale. They have already been sold to Him for Whom they were meant"). A countless stream of devotees arrive at the well-known Dar-ul-Ehsan sanctuary and receive, by His grace, spiritual instructions from among the fourteen Sufi orders of which Barkat Ali is a teaching master, or shaykh. Maa shaa' Allaah! The qualities and attributes of Sufi Barkat Ali could be enumerated further, but anyone who views his life with an open mind must conclude that he h as exceeded the usual range of human accomplishments. He is now in his seventy-sixth year. 
[This formula is also very important for healing- conveying protection against any illness for the day it is recited.]
Begin always with:
Laa ilaaha illa-Llaah, Muhammadun Rasoolu-Llaah
A'oodhu bi-Llaahi min ash-shaytaan ir-rajeem.
[The formula for the Keys of the Treasures of the Heavens and the Earth may be recited 21 times after each daily prayer and requires not more than three or four minutes to do so.]
Laa ilaaha illa-Llaah wa-Llaahu Akbar
wa Subhaana-Llah wal Hamduli-Llaah w-Astaghfiru-Llaah
Alladhi laa illaaha illaa Hu
al-Awwalu wal-Aakhiru waz-Zaahiru wal-Baatinu
yuhyi wa yumeetu wa huwa Hayyun laa yamootu
wa huwa 'alaa kulli shay'in Qadeer
1. The Hadith master Imam as-Suyuti said that this hadith is fabricated, but its results may speak otherwise. Many Sufis consider it as one of the most powerful and effective prayers in Islam. Allahu A'lam. (My footnote)
2. Source: The Book of Sufi Healing, pg 155-157
Note: Hadrat Barkat Ali has since passed away (in 1997).