Allah Almighty says: {When you enter houses, give greetings of peace upon each other - a greeting from Allah, blessed and good} [Surat an-Nūr: 61]
861/1 - Anas (may Allah be pleased with him) reported that the Prophet (may Allah’s peace and blessings be upon him) said to him: “O son, when you enter your house, greet your family, for it will be a blessing for you and your household.” [Narrated by Al-Tirmidhi; he classified it as Hasan Sahīh (sound and authentic)]
1) Saying the greeting of peace to one’s household brings about blessing and cordiality.
2) The Prophet (may Allah’s peace and blessings be upon him) treated his servant Anas kindly and mercifully. He addressed him “O son!”
3) A man may address a child saying “O son”, even if he is not his son, by way of showing kindness.