Greet those you know and those you don’t know
Abdullah bin Amr bin Al-as (radi Allahu anhu) reported: A man asked the Messenger of Allah (sal Allahu alaihi wa sallam): “Which act in Islam is the best?” He (sal Allahu alaihi wa sallam) replied, “To give food, and to greet everyone, whether you know or you do not.”
[Sahih Al-Bukhari and Muslim]
We benefit from the above Hadith that feeding the poor and destitute is an act of goodness and that Greeting your fellow Muslim by saying ‘As-Salamu ‘Alaikum’ (which is the minimum) whether an acquaintance or a stranger, is a good manner too.
Both of these acts generate mutual love and remove hatred and ill feelings from the hearts. All other forms of greetings do not substitute for this great Islamic greeting.
And Allah knows best!