Although all the good deeds are required in the first ten days of Dhul-Hijjah; yet remembering Allah Almighty is of special significance; Al-Bukhari narrated from Ibn Abbas, may Allah be pleased with him: said: "(And remember Allah during the known Days), means the ten days. For (And remember Allah during the [specific] numbered Days), means the Days of Tashriq (11-12-13th of Dhul-Hijjah).

Ibn Omar, and Abu Huraira, may Allah be pleased with them, have been used to go out to the markets in the ten days reciting the Takbir -- Allahu Akbar, Allahu Akbar, so that people do the same. Also, Muhammad ibn `Ali recited Takbir behind the Camel.

This narration of Al-Bukhari cited that Ibn Abbas, may Allah be pleased with him, has interpreted the known days to mean the first ten days of Dhul-Hijjah, and interpreted the [specific] numbered days as the days of Tashriq, and the main deed Allah Almighty asked for during the certain and [specific] numbered deeds is remembrance as Quranic verses read the following: (That they may witness benefits for themselves and mention the name of Allah on known days over what He has provided for them of [sacrificial] animals. So eat of them and feed the miserable and poor.), Al-Hajj, 28, and (And remember Allah during [specific] numbered days. Then whoever hastens [his departure] in two days – there is no sin upon him; and whoever delays [until the third] – there is no sin upon him – for him who fears Allah . And fear Allah and know that unto Him you will be gathered.), Al-Baqarah, 203.

As demonstration to this is the action made by ibn Umar and Abu-Hurairah, may Allah be pleased with them. Therefore, Takbir during these days is a prophetic Sunnah. Another narration widen the scope of Takbir during the ten days has been related by Imam Ahmad on the authority of ibn Umar that the Prophet Muhammad (PBUH) said: (There are no days greater and more beloved to Allah then these ten days of Dhul-Hijjah, so increase in them your declaration of the oneness of Allah, your exaltation of Him, and your praise of Him.)

Let’s be keen to observe this blessed sunnah during these days.

http://300035.dotdothktrade.tech/en/artical/28803/90-sunnah-Takbir-during-ten-days