In Quran chapter Noor, verse 61, Allah guides us:
So when you enter houses, greet your people with a salutation from Allah, blessed (and) goodly;
Al-Noor [24:61]
i.e. say salam when enter the home.
According to Hadith, a companion of the Last Prophet Muhammad (Peace Be Upon Him) came and revealed the financial crisis, the Last Prophet of Allah said that if you enter the home say salam, even there is nobody at home, and the recite Surah-e-Ikhlas once.
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