Hawzah News Agency – The merciful prophet of Islam, peace be upon him and his household says:

إنَّ أبخَلَ الناسِ مَن بَخِلَ بِالسلامِ.

'The most miserly of all people is he who withholds his greeting.'

Source: Amali al-Tusi, p. 89, no. 136