Sunan an-Nasa'i, Volume 4, Book 30, Hadith 3681 (DarusSalam) ⓘ
It was narrated from Abu Hurairah that the Messenger of Allah said: "When a man dies all his good deeds come to an end except three: Ongoing charity (Sadaqah Jariyah), beneficial knowledge and a righteous son who prays for him."
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ حَدَّثَنَا إِسْمَاعِيلُ، قَالَ حَدَّثَنَا الْعَلاَءُ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " إِذَا مَاتَ الإِنْسَانُ انْقَطَعَ عَمَلُهُ إِلاَّ مِنْ ثَلاَثَةٍ مِنْ صَدَقَةٍ جَارِيَةٍ وَعِلْمٍ يُنْتَفَعُ بِهِ وَوَلَدٍ صَالِحٍ يَدْعُو لَهُ " .
also referenced under: Hadith 3651 (Reference) & Book 30, Hadith 41 (In-Book)