Majma al-Zawaid — Hadith 11370

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrated this as a marfu' hadith from the Prophet (peace and blessings be upon him); he said: "Indeed Allah Almighty will raise the offspring of the believer to him, into his rank, even though that offspring is lower than the believer in deeds; the reason for this will be so that the eyes of that believer are cooled by them." Then he recited this verse: "Those who believed and whose offspring followed them in faith" Then he said: "We will not reduce anything from the fathers because of what We give the sons."
Al-Bazzar recorded it; its chain contains the narrator Qays bin al-Rabi', whom Shu'bah and al-Thawri declared thiqah (trustworthy), and there is weakness in him.