Once Allah's Messenger (ﷺ) remained behind us in a journey. He joined us while we were performing ablution for the `Asr prayer which was over-due. We were just passing wet hands over our feet (not washing them properly) so the Prophet (ﷺ) addressed us in a loud voice and said twice or thrice, "Save your heels from the fire."
Sahih al-Bukhari Book 3, Hadith 38
← Previous Hadith Whenever the Prophet (ﷺ) spoke a sentence (said a thing), he used to repeat it thrice so that the people could understand it properly from him and whenever he asked permission to enter, (he knocked the door) thrice with greeting.

Sahih al-Bukhari Book 3, Hadith 37 Next Hadith → Allah's Messenger (ﷺ) said "Three persons will have a double reward:

1. A Person from the people of the scriptures who believed in his prophet (Jesus or Moses) and then believed in the Prophet (ﷺ) Muhammad (i .e. has embraced Islam).

2. A slave who discharges his duties to Allah and his master.

3. A master of a woman-slave who teaches her good manners and educates her in the best possible way (the religion) and manumits her and then marries her."

Sahih al-Bukhari Book 3, Hadith 39