Nature
"And it is He Who spread out the earth, and placed therein firm mountains and rivers and of every kind of fruits He made Zawjain Ithnain (two in pairs-may mean two kinds or it may mean: of two varieties, e.g. black and white, sweet and sour, small and big).He brings the night as a cover over the day. Verily, in these things, there are Ayat (proofs, evidences, lessons, signs, etc.) for people who reflect." (Surat Ar-Ra'd (The Thunder): 3);