It is narrated from Hazrat Abu Umamah (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: Four types of people continue to receive reward even after their death: (one) a person who performed a good deed whose effect continues, (two) a person who gave ongoing charity, (three) a person who left behind righteous children who pray for him.
Hadith Referenceمسند احمد / مسند الأنصار رضي الله عنهم / 22318
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف لإبهام الراوي له عن أبى أمامة ، ورواية ابن المبارك عن ابن لهيعة صالحة