Al-Hafidh, Ibn Hajar (r) says:
❝The scholars are in agreement that it is recommended to perform the Takbir (al-Muqayyad)* after the prayers on these days (of Dhu-l Hijjah). There is nothing authentic regarding it from the Messenger (peace and blessings be upon him), but there are narrations from the Sahabah and those who came after them, and this is the established practice of the Ummah.❞
[Fath al-Bari, Sharh Sahih al-Bukhari]
*Takbir al-Muqayyad are the Takbirat performed at the end of the five daily prayers in congregation.