he sealed / he concluded
Form I verb. Noun: خَاتَمٌ (seal/ring). خَاتِمُ النَّبِيِّينَ (Seal of the Prophets, 33:40). Present: يَخْتِمُ.
Muhammad ﷺ is called Khātam an-Nabiyyīn (Seal of the Prophets) - the final prophet, after whom no new prophet will come.