The Messenger of Allah ﷺ said, "Follow up Hajj with Umrah, for following one with the other removes poverty and sins just as the bellows removes impurities from iron."
حدثنا عبد الرزاق أخبرنا ابن جريج قال عن عاصم بن عبيد الله
قال رسول الله ﷺ تابعوا بين الحج والعمرة فإن متابعة بينهما تنفي الفقر والذنوب كما ينفي الكير خبث الحديد
Its isnad is hasan. It came earlier at 3669, and it is found in Tirmidhi 3/166, no. 810, where he said, hasan sahih, and in Nasai 5/115, no. 2630, both from Ibn Masud, and in Ibn Majah 2/964, no. 2887, like Ahmad.