Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated that Sayyidah Umm Sulaym (may Allah be pleased with her) came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah, Abu Talhah and his son have gone for Hajj on their water-carrying camel and left me behind. He (peace and blessings be upon him) said: "O Umm Sulaym, an Umrah in Ramadan stands in place of a Hajj."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11274