The Prophet (ﷺ) was vigilant one night and when he reached Medina, he said, "Would that a pious man
from my companions guard me tonight!" Suddenly we heard the clatter of arms. He said, "Who is
that? " He (The new comer) replied, " I am Sa`d bin Abi Waqqas and have come to guard you." So,
the Prophet (ﷺ) slept (that night).
Sahih al-Bukhari Book 56, Hadith 100