The Prophet ﷺ said, "My example and the example of the prophets before me is like that of a man who built a building, making it beautiful and elegant, except for the place of a single brick in one of its corners. People began to walk around it, marveling at it and saying, 'If only this brick were placed!' I am that brick, and I am the seal of the prophets."
حدثنا سليمان بن داود قال أخبرنا إسماعيل عن ابن دينار يعني عبد الله عن أبي صالح السمان
أن النبي ﷺ قال مثلي ومثل الأنبياء من قبلي كمثل رجل بنى بنيانا فأحسنه وأجمله إلا موضع لبنة من زاوية من زواياه فجعل الناس يطوفون به ويعجبون له ويقولون هلا وضعت هذه اللبنة قال فأنا تلك اللبنة وأنا خاتم النبيين
Its isnad is sahih. It preceded at 7479, and it is found in Bukhari 6/558, no. 3535, Fath, in the Book of Virtues, the Seal of the Prophets, and Muslim 4/1791, no. 2286, in the Book of Virtues, mention of him being the Seal of the Prophets.