Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) has transmitted this hadith from the Prophet (peace and blessings be upon him) as a marfu' (Prophetic) hadith. He said: "The pilgrim will intercede for four hundred people of his household (the narrator is in doubt about one word here), and he emerges from his sins as he was on the day his mother gave birth to him."
Al-Bazzar recorded it. Its chain contains a narrator who has not been named. Further on, hadiths will come about meeting the pilgrims and requesting their supplication, if Allah wills.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الحج / 5289