Speaking about the religion without knowledge
Shaykhul Islaam Ahmad ibn Taymeeyah 728AH (May Allah have mercy on him) said, ﻣﻦ ﺗﻜﻠﻢ ﻓﻲ ﺍﻟﺪﻳﻦ ﺑﻼ ﻋﻠﻢ ﻛﺎﻥ ﻛﺎﺫﺑﺎً، ﻭﺇﻥ ﻛﺎﻥ ﻻ ﻳﺘﻌﻤﺪ ﺍﻟﻜﺬﺏ “Whoever speaks about the religion without knowledge is a liar even if he doesn’t intend to lie.” Source: Majmu’ Fataawa 10/449