Hawzah News Agency – The commander of the faithful, Imam Ali peace be upon him says:

السلامُ سَبعونَ حَسَنةً، تِسعَةٌ وسِتُّونَ لِلمُبتَدي وواحِدَةٌ لِلرّادِّ.

'The greeting is rewarded the worth of seventy good deeds, sixty-nine of which are rewarded to the initiator and one to the reciprocator [of the greeting].'

Source: Bihar al-Anwar, v. 76, p. 11, no. 46