Narrated ‘Abdullah [رحمه الله] : Allah’s Messenger (ﷺ) said, “The best people are those of my generation, and then those who will come after them (the next generation), and then those who will come after them (i.e. the next generation), and then after them, there will come people whose witness will precede their oaths, and whose oaths will precede their witness.” (Sahih Bukhari, Muslim and al-Tirmidhi)
Did the Caliphs (Abu Bakr, Umar, Uthman & Ali) or Sahabahs (companions) celebrate the Mawlid – NO, by Allaah! Is it because they were not aware of its importance, or did they not truly love the Prophet (ﷺ)? No one would say such a thing except one who has gone astray and is leading others astray.
Did any of the Imaams (Abu Haneefah, Maalik, al-Shaafi’i, Ahmad, al-Hasan al-Basri) celebrate the Mawlid or command others to do it or say that it was good? By Allaah, NO! It was not even mentioned during the first and best three centuries.
The celebration of the Prophet’s birthday appeared many centuries later, when many of the features of true religion had vanished and bid’ah had become widespread.