It is Sunnah to say Takbeer(“Allaahu akbar”), Tahmeed (“Al-hamdu Lillaah”), Tahleel (“La ilaha ill-Allaah”) and Tasbeeh (“Subhaan Allaah”) during the first ten days of Dhu’l-Hijjah, and to say it loudly in the mosque, the home, the street and every place where it is permitted to remember Allaah and mention His name out loud, as an act of worship and as a proclamation of the greatness of Allaah, may He be exalted.
Men should recite these phrases out loud, and women should recite them quietly.
Allaah says (interpretation of the meaning):”That they might witness things that are of benefit to them (i.e., reward of Hajj in the Hereafter, and also some worldly gain from trade, etc.), and mention the name of Allaah on appointed days, over the beast of cattle that He has provided for them (for sacrifice)…”
The majority of scholars agree that the “appointed days” are the first ten days of Dhu’l-Hijjah, because of the words of Ibn ‘Abbaas (may Allaah be pleased with him and his father):
“The ‘appointed days’ are the first ten days (of Dhu’l-Hijjah).”
The Takbeer may include the words “Allaahu akbar, Allaahu akbar, la ilaaha ill-Allaah; wa Allaahu akbar wa Lillaahi’l-hamd(Allaah is Most Great, Allaah is Most Great, there is no god but Allaah; Allaah is Most Great and to Allaah be praise),” as well as other phrases.
ThisTakbeer should be pronounced loudly, in order to revive the Sunnah and as a reminder to the negligent.
There is sound evidence that Ibn ‘Umar and Abu Hurayrah (may Allaah be pleased with them) used to go out in the marketplace during the first ten days of Dhu’l-Hijjah, reciting Takbeer, and the people would recite Takbeer when they heard them.
Reviving aspects of the Sunnah that have been virtually forgotten is a deed that will bring an immense reward, as is indicated by the words of the Prophet (peace and blessings of Allaah be upon him): “Whoever revives an aspect of my Sunnah that is forgotten after my death, he will have a reward equivalent to that of the people who follow him, without it detracting in the least from their reward.”
(Reported by al-Tirmidhi, 7/443)