Hadith: "I was Khatam al-Nabiyyin even when Adam (as) was still in the very early stages of his creation." Ibn Hibban and al-Hakim authenticated it. - Fath al-Bari sharh Sahih al-Bukhari

Fath al-Bari seal of the prophet when Adam cover - Ibn Hajar
I was Khatam al-Nabiyyin even when Adam was in the early stages of his creation - Fath al-Bari