(4) باب بَيَانِ الإِيمَانِ الَّذِي يُدْخَلُ بِهِ الْجَنَّةُ وَأَنَّ مَنْ تَمَسَّكَ بِمَا أُمِرَ بِهِ دَخَلَ الجَنَّةَ
It is narrated on the authority of Jabir that a man once said to the Messenger of Allah (ﷺ):
Shall I enter Paradise in case I say the obligatory prayers, observe the (fasts) of Ramadan and treat that as lawful which has been made permissible (by the Shari'ah) and deny myself that what is forbidden, and make no addition to it? He (the Holy Prophet) replied in the affirmative. He (the inquirer) said: By Allah, I would add nothing to it.
Reference: Sahih Muslim 15 c
In-book reference: Book 1, Hadith 18
USC-MSA web (English) reference(deprecated numbering scheme): Book 1, Hadith 17