Mishkat al-Masabih 568
Ibn Mas'ud said:
I asked the Prophet which action is dearest to God and he replied, “Prayer at its proper time.” I asked what came next, and he replied that it was kindness to parents. I asked what came next and he replied that it was jihad in God's path. He said, “He told me of them, and if I had asked for more he would have told me more.” 

(Bukhari and Muslim.)
وَعَنْ عَبْدِ اللَّهِ بْنِ مَسْعُودٍ قَالَ: سَأَلْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَي الْأَعْمَال أحب إِلَى الله قَالَ: «الصَّلَاةُ لِوَقْتِهَا» قُلْتُ ثُمَّ أَيُّ قَالَ: «بِرُّ الْوَالِدَيْنِ» قُلْتُ ثُمَّ أَيُّ قَالَ: «الْجِهَادُ فِي سَبِيلِ اللَّهِ» قَالَ حَدَّثَنِي بِهِنَّ وَلَوِ استزدته لزادني