The Prophet ﷺ said, "A person's messenger sent to another person serves as his permission to enter."
عن النبي ﷺ قال: رسول الرجل إلى الرجل إذنه.
No references are available.
Abu Dawud (5189) and Bukhari in Adab al-Mufrad (1076) both narrated it from Musa bin Ismail, who said, Hammad bin Salama narrated to us, from Habib and Hisham, from Muhammad, from Abu Hurairah, who related it. Its isnad is sahih, and Muhammad here is Ibn Sirin, while Habib is Ibn Shahid.