ADAB 1005:

Thabit ibn 'Ubayd said, "I came to a group which included 'Abdullah ibn 'Umar who said, 'When you greet, make it clearly audible, for it is a greeting from Allah containing great blessing.:

الأدب المفرد ١٠٠٥:

أَتَيْتُ مَجْلِسًا فِيهِ عَبْدُ اللهِ بْنُ عُمَرَ، فَقَالَ‏:‏ إِذَا سَلَّمْتَ فَأَسْمِعْ، فَإِنَّهَا تَحِيَّةٌ مِنْ عِنْدِ اللهِ مُبَارَكَةً طَيْبَةً‏.‏


Sound (Albānī)
al-Adab al-Mufrad > Greetings > § Make it heard when you greet
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