We set out calling out the talbiyah for hajj. When we arrived in Makkah, the Messenger of Allah ﷺ commanded us to make it an umrah instead. He said, "Had I known at the start what I have come to know later, I would have made it an umrah. But I have brought the sacrificial animal with me, so I have combined hajj and umrah together."
حدثنا أحمد بن عبد الملك حدثنا زهير حدثنا أبو إسحاق عن أبي أسماء الصيقل
خرجنا نصرخ بالحج فلما قدمنا مكة أمرنا رسول الله ﷺ أن نجعلها عمرة وقال لو استقبلت من أمري ما استدبرت لجعلتها عمرة ولكن سقت الهدي وقرنت الحج والعمرة
Its isnad is sahih, for several reasons. First, because Abu Asma the Sword-sharpener was narrated from by a trustworthy narrator. Second, he is trustworthy, for Ibn Hibban mentioned him among the trustworthy narrators, though some considered him unknown, among them Ibn Hajar in Taqrib, because Abu Zura was asked about him and said, "I do not know his name," and in some references this has been corrupted to "I do not know him." Perhaps this was the wording with Ibn Hajar, or perhaps he considered him unknown because no one other than Abu Ishaq narrated from him, but in fact narrations from others besides Abu Ishaq have been mentioned for him. See Jarh 9/333 and Thiqat 5/178. Third, because the hadith has been narrated through various routes and is sahih, as already discussed at 12881 and all its cross-references.