Many people have doubts about celebrating the Milad of the Holy Prophet (Sallallahu alaihi wa sallam). In the following lines, proof of doing so is presented from the Hadith.
The following Hadith is mentioned in Sahih Bukhari and many other books of Hadith with a slight change in wording. Some Hadith are brief and some are detailed. The Hadith in Sahih Bukhari is:
Translation of Hadith: Hadhrat 'Urwah says: Thuwayba was the slave of Abu Lahab. Abu Lahab had set her free to nurse the Holy Prophet (Sallallahu alaihi wa sallam). After Abu Lahab died, some of his family members saw him in a dream in the worst possible state. He was asked: What did you get? Abu Lahab said: After separating from you, I never got any peace, but only because of setting Thuwayba free, I am refreshed through this (his finger). (Sahih Bukhari, Kitab Un Nikah, Vol. 2, Pg No. 764)
In the explanation/commentary of this Hadith, the Imams, Hadhrat Allama Badruddin 'Aini and Imam Ibn Hajr 'Asqalani, narrate other lengthy versions of this Hadith on the authority of other books. Here we present what our Hadhrat Badruddin 'Aini Hanafi (May Allah shower His Mercy on him) writes in his famous commentary on Sahih Bukhari, Umdatul Qari, Vol. 14, Pg No. 45:
Translation: Hadhrat Abbas (May Allah be well pleased with him) says: I saw Abu Lahab in a dream 1 year after his death. I saw him in the worst possible state. He said: I didn’t get any relief after I separated from you. However every Monday, my punishment is lightened. Hadhrat Abbas (May Allah be well pleased with him) says: That is because the Holy Prophet (Sallallahu alaihi wa sallam) was born on this day and Thuwayba had given this good news to Abu Lahab and he had set her free. ('Umdatul Qari, Vol. 14, Pg No. 45)
With a slight change in wording, this Hadith is present in the following books of Hadith:
Sunan Kubra, Hadith No: 14297
Musannaf Abdur Razzaq, Vol. 7, Hadith No: 13456
Jame' Ul Ahadith Wal Maraseel, Hadith No: 43545
Kanz Ul Ummal, Hadith No: 15725