From Sahih Bukhari (Hadith 2885):
Narrated `Aisha: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)
Reference: Bukhari 2885