Sunan Ibn Majah 241
سنن ابن ماجه#241SahihAbdullah bin Abu Qatadah narrated that his father said:"The Messenger of Allah said: 'The best things that a man can leave behind are three: A righteous son who will pray for him, ongoing charity whose reward will reach him, and knowledge which is acted upon after his death.'" (Hasan) Another chain with similar wording
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Zubair Ali ZaiHasan