Sunan an-Nasa'i, Hadith 3130 ⓘ
It was narrated that Abu Hurairah said: "A man asked the Messenger of Allah which deed is best. He said: 'Faith in Allah.' He said: 'Then what?' He said: 'Jihad in the cause of Allah.' He said: 'Then what?' He said: 'Hajjun Mabrur.'" [1] [1] Hajj, that is accepted, or free of sin.
أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا عَبْدُ الرَّزَّاقِ، قَالَ حَدَّثَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، عَنِ ابْنِ الْمُسَيَّبِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ سَأَلَ رَجُلٌ رَسُولَ اللَّهِ صلى الله عليه وسلم أَىُّ الأَعْمَالِ أَفْضَلُ قَالَ " إِيمَانٌ بِاللَّهِ " . قَالَ ثُمَّ مَاذَا قَالَ " الْجِهَادُ فِي سَبِيلِ اللَّهِ " . قَالَ ثُمَّ مَاذَا قَالَ " حَجٌّ مَبْرُورٌ " .
also referenced under: Book 25, Hadith 46 (In-Book) & Volume 4, Book 25, Hadith 3132 (DarusSalam)