Well they are not the only ones who belive the Earth is flat.
Earth has four corners, and floats on water (Isa 11:12, Ps 24:2, 136:6, Rev 7:1). Earth is a circular disk (Isa 40:22). Earth is flat (these verses were used for centuries by the church to prove this: 1 Chron 16:30, Ps 93:1, Jer 10:13, Dan 4:10- 11, Zech 9:10, Matt 4:8, Rev 1:7, Isa. 40:22). Earth does not move (Ps 93:1, 96:10, 104:5, 1 Chr 16:30)."
In 1993, Shaikh Abd Al-‘Azeez bin Baaz, the supreme religious authority of Saudi Arabia, declared that the earth is flat, and that anyone saying otherwise is an atheist deserving of punishment [
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