The Prophet ﷺ performed Umrah four times, one of which was in Rajab.
حدثنا أحمد بن منيع حدثنا الحسن بن موسى حدثنا شيبان عن منصور عن مجاهد
أن النبي ﷺ اعتمر أربعا إحداهن في رجب
Bukhari also narrated it in the Book of Umrah, chapter "How many times did the Prophet ﷺ perform Umrah," hadith no. 1775, from the hadith of Mansur through the same chain.