Narrated 'Ursa; Thuwaiba was the freed slave girl of Abu Lahb whom he had manumitted, and then she suckled the Prophet. When Abu Lahb died, one of his relatives saw him in a dream in a very bad state and asked him, "What have you encountered?" Abu Lahb said, "I have not found any rest since I left you, except that I have been given water to drink in this (the space between his thumb and other fingers) and that is because of my manumitting Thuwaiba."
Abu Lahab freed Thuwaiba on joy at birth of Prophet (salallaho alaihi wasalam), even the worst of Kufaar and greatest of enemies is given relaxation in his Adhaab due to freeing Thawaiba by pointing with his finger, so Imagine the situation of a momin who rejoices on Mawlid
Volume 7, Book 62, Number 38: (Sahih Bukhari)
Narrated 'Ursa; Thuwaiba was the freed slave girl of Abu Lahb whom he had manumitted, and then she suckled the Prophet. When Abu Lahb died, one of his relatives saw him in a dream in a very bad state and asked him, "What have you encountered?" Abu Lahb said, "I have not found any rest since I left you, except that I have been given water to drink in this (the space between his thumb and other fingers) and that is because of my manumitting Thuwaiba."
Abu Lahab freed Thuwaiba on joy at birth of Prophet (salallaho alaihi wasalam), even the worst of Kufaar and greatest of enemies is given relaxation in his Adhaab due to freeing Thawaiba by pointing with his finger, so Imagine the situation of a momin who rejoices on Mawlid