Groaning invalidates the prayer, except if the person is sick and cannot control himself from groaning and sighing; because his groaning then is like sneezing if it results in letters. It is reported from Ibn Abbas, may Allah be pleased with him, that the Prophet, peace be upon him, said: ((Blowing in prayer is speech)), in Musannaf Ibn Abi Shaybah 2: 67, and Musannaf Abd al-Razzaq 2: 189, and its chain is authentic. See: I'la al-Sunan 5: 51. And from Abu Huraira, may Allah be pleased with him: he said: ((Blowing in prayer is speech)), in Musannaf Abd al-Razzaq 2: 189. See: Fath Bab al-Inayah 1: 302.