Kulayb narrates that he heard Abu Hurayra say that ‘The Messenger of Allah ﷺ said:
“Whoever sees me in a dream has truly seen me because Satan cannot impersonate me.” ‘
Kulayb then said ‘I related this to Ibn Abbas and I said to him, “I saw him (The Messenger of Allah ﷺ) in my dream and I remembered Hasan ibn Ali…He resembles him!”.
Ibn Abbas said ‘Indeed he does!’.
Sham’ail al-Tirmidhi (Hadith 409)
Abu Hurayra and Ibn Abbas were companions of the Messenger of Allah ﷺ however the one who saw the dream (Kulayb) was not a companion. He had not seen the Prophet ﷺ in person however he had seen Imam al-Hasan (the grandson of the Prophet ﷺ). From this Hadith and several others, we learn that Imam al-Hasan resembled the Prophet ﷺ in appearance.
In a famous narration, Imam Ali (the father of al-Hasan and al-Husayn) said:
Al-Hasan resembles The Messenger of Allah ﷺ from head to chest and al-Husayn resembles the Prophet ﷺ in what is below that.
Tirmidhi and Ibn Hibban
Sayiduna Anas bin Malik said:
There is nobody who resembles The Prophet ﷺ more than Hasan bin Ali.
Bukhari
There is also a wonderful incident where we see Sayiduna Abu Bakr and Sayiduna Ali sharing a light hearted moment regarding al-Hasan:
Uqba bin Al-Harith said that:
I saw Abu Bakr whilst he was carrying al-Hasan and he was saying:
“May my father be sacrificed for you; you resemble the Prophet and you don’t resemble Ali!”
And (upon hearing this) Ali was laughing.’
Bukhari
Orthodox Muslim 