From Sahih Muslim (Hadith 5963):
Jabir reported Allah's Messenger (ﷺ) as saying:The similitude of mine and that of the Apostles is like that of a person who built a house and he completed it and made it perfect but for the space of a brick. People entered therein and they were surprised at it and said: Had there been a brick (it would have been complete in all respects). Allah's Messenger (ﷺ) said: I am that place where the brick (completing the building is to be placed), and I have come to finalise the chain of Apostles
Reference: Muslim 5963