Hawzah News Agency – Imam al-Sadiq (AS) narrated from his forefathers (AS) that the Prophet (SAWA) said,

مَن بَدَأ بِالكَلامِ قَبلَ السلامِ فلا تُجِيبُوهُ. وقالَ عليه السلام: لا تَدعُ إلى‏ طَعامِكَ أحَداً حتّى يُسَلِّمَ.

'Do not answer the one who begins to talk before having greeted you with peace', and he (AS) said, 'Do not allow anybody to partake of your food until they have greeted with peace.'

Source: al-Khisal, p. 19, no. 67