I saw the 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, who classified the hadith as Hasan Sahih].
"لا تقل عليك السلام؛ فإن عليك السلام تحية الموتى"