What is the secret of the number 7 and its multiples in the Holy Qur’aan and Sunnah?
Question

                What is the secret of the number 7 in the Qur’aan and hadeeth?.
Praise be to Allah.Undoubtedly the Qur’aan is 
    miraculous, and there are many facets to its miraculous nature, such as 
    linguistic, legislative, and so on. Its challenge to mankind and the jinn to 
    produce something similar to it still stands. Allaah says (interpretation of 
    the meaning): 
“Say: If the mankind and 
    the jinn were together to produce the like of this Qur’aan, they could not 
    produce the like thereof, even if they helped one another”
[al-Isra’ 17:88]. 
Ibn al-Qayyim discussed the 
    number 7 in his book Zaad al-Ma’aad fi Huda Khayr al-‘Ibaad (4/90) 
    when he discussed the hadeeth in al-Saheehayn: “The one who eats seven dates 
    of al-‘Aaliyah in the morning will not be harmed that day by poison or 
    witchcraft.” He said: As for specifying the number seven, it has to do with 
    the creation and sahr’i commands of Allaah. Allaah created seven heavens, 
    seven earths and seven days, and man’s creation is completed in seven 
    stages; Allaah has prescribed that His slaves should walk around the Ka’bah 
    seven times (tawaaf) and go back and forth between Safa and Marwah seven 
    times (saa’i), and stone the jamaraat with seven pebbles each, and the 
    takbeeraat of Eid are seven in the first rak’ah. The Prophet  (peace and 
    blessings of Allaah be upon him) said: “Instruct your children to pray when 
    they are seven.” When the boy reaches the age of seven he should be given 
    the choice between his parents according to one report, and according to 
    another report, his father has more right to him than his mother; according 
    to a third report his mother has more right to him. When he was sick, the 
    Prophet  (peace and blessings of Allaah be upon him) ordered that water 
    from seven skins be poured on him. Allaah sent the wind against the people 
    of ‘Aad for seven days. The Prophet  (peace and blessings of Allaah be 
    upon him) asked Allaah to help him by sending upon his people seven (years) 
    like the seven years of Yoosuf – i.e., seven years of famine. Allaah likened 
    the reward of one who gives charity to a grain that produces seven ears, in 
    each of which are one hundred grains. The number of ears of grain seen by 
    the companion of Yoosuf (in the dream) was seven, the number of years for 
    which they were cultivated was seven, and (the reward for charity) is 
    multiplied seven hundred fold or more. Seventy thousand of this ummah will 
    be admitted to Paradise without being brought to account. 
Then Ibn al-Qayyim 
    commented: Undoubtedly this number has some special qualities that are not 
    shared by other numbers. … Allaah knows best about His wisdom, laws and 
    decree in singling out this number. End quote.  
Based on this, the correct 
    view is to refrain from indulging in discussion of the reason why this 
    number is singled out for mention, except on the basis of clear, sound 
    evidence. 
For more information please 
    see the answer to question no. 69741. 
And Allaah knows best.