Abu Juraiy Al-Hujaimi (May Allah be pleased with him) reported:
I saw Messenger of Allah (ﷺ) and said: "Alaikas-Salamu ya Rasulallah! (Upon you be peace, O Messenger of Allah)!" He said, "Do not say: 'Alaikas-Salamu (Upon you be peace).' This is the Salam to the dead."[Abu Dawud and At-Tirmidhi].
App reference: Book 6, Hadith 12
Arabic/English book reference: Book 6, Hadith 856