And God said,
Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:
All Commentaries on Genesis 1:14 Go To Genesis 1
Ephrem The Syrian
AD 373
After Moses spoke about the gathering of the waters and about the sprouting of the vegetation on the earth on the third day, he turned to write about the lights that were created in the firmament saying, "And God said, 'Let there be lights in the firmament of the heavens to separate the day from the night'," [ Gen1:14 ] that is, one to rule over the day and the other [ to rule ] over the night.
That [ God ] said, "Let them be for signs," [ Gen1:14 ] [ refers to ] measures of time, and "let them be for seasons," clearly indicates summer and winter. "Let them be for days," are measured by the rising and setting of the sun, and "let them be for years," are comprised of the daily cycles of the sun and the monthly cycles of the moon.