“Nature and Nature's laws lay hid in night:
God said, "Let Newton be!"”

Source: The Mote in God's Eye (1974), Chapter 47 “Homeward Bound” (p. 445)

The earliest published source found on google books that attributes this to Euclid is A Mathematical Journey by Stanley Gudder (1994), p. xv http://books.google.com/books?id=UiOxd2-lfGsC&q=%22mathematical+thoughts%22+euclid#search_anchor. However, many earlier works attribute it to Johannes Kepler, the earliest located being in the piece "The Mathematics of Elementary Chemistry" by Principal J. McIntosh of Fowler Union High School in California, which appeared in School Science and Mathematics, Volume VII ( 1907 http://books.google.com/books?id=kAEUAAAAIAAJ&pg=PR3#v=onepage&q&f=false), p. 383 http://books.google.com/books?id=kAEUAAAAIAAJ&pg=PA383#v=onepage&q&f=false. Neither this nor any other source located gives a source in Kepler's writings, however, and in an earlier source, the 1888 Notes and Queries, Vol V., it is attributed on p. 165 http://books.google.com/books?id=0qYXAQAAMAAJ&pg=PA165#v=onepage&q&f=false to Plato. It could possibly be a paraphrase of either or both of the following to comments in Kepler's 1618 book Harmonices Mundi (The Harmony of the World)': "Geometry is one and eternal shining in the mind of God" and "Since geometry is co-eternal with the divine mind before the birth of things, God himself served as his own model in creating the world".
Misattributed

Attributed to Kepler in some sources (though more recent sources often attribute it to Euclid), such as Mathematically Speaking: A Dictionary of Quotations edited by Carl C. Gaither and Alma E. Cavazos-Gaither (1998), p. 214 http://books.google.com/books?id=4abygoxLdwQC&lpg=PP1&pg=PA214#v=onepage&q&f=false. The earliest publication located that attributes the quote to Kepler is the piece "The Mathematics of Elementary Chemistry" by Principal J. McIntosh of Fowler Union High School in California, which appeared in School Science and Mathematics, Volume VII ( 1907 http://books.google.com/books?id=kAEUAAAAIAAJ&pg=PR3#v=onepage&q&f=false), p. 383 http://books.google.com/books?id=kAEUAAAAIAAJ&pg=PA383#v=onepage&q&f=false. Neither this nor any other source located gives a source in Kepler's writings, however, and in an earlier source, the 1888 Notes and Queries, Vol V., it is attributed on p. 165 http://books.google.com/books?id=0qYXAQAAMAAJ&pg=PA165#v=onepage&q&f=false to Plato. Expressions that relate geometry to the divine "mind of God" include comments in the Harmonices Mundi, e.g., "Geometry is one and eternal shining in the mind of God", and "Since geometry is co-eternal with the divine mind before the birth of things, God himself served as his own model in creating the world".
Disputed quotes

D.H. v. H.H. http://caselaw.findlaw.com/al-supreme-court/1303306.html (February 15, 2002), quoted in [2017-09-29, Michelle Goldberg, How Donald Trump Opened the Door to Roy Moore, The New York Times, https://www.nytimes.com/2017/09/29/opinion/donald-trump-roy-moore.html]

Source: The Christian Agnostic (1965), p.106 (Augustine: The City of God. 21:8)

Maria Mitchell: Life, Letters and Journals http://www.gutenberg.org/cache/epub/10202/pg10202.html (1896).

As quoted in Truth Against the World : Frank Lloyd Wright speaks for an organic architecture (1987) edited by Patrick J. Meehan <!-- p. 29 -->
Context: God is the great mysterious motivator of what we call nature and it has been said often by philosophers, that nature is the will of God. And, I prefer to say that nature is the only body of God that we shall ever see. If we wish to know the truth concerning anything, we'll find it in the nature of that thing.

Opening lines, p. 104
Variant translations:
What is God-given is called nature; to follow nature is called Tao (the Way); to cultivate the Way is called culture.
As translated by Lin Yutang in The Importance of Living (1937), p. 143
What is God-given is called human nature.
To fulfill that nature is called the moral law (Tao).
The cultivation of the moral law is called culture.
As translated by Lin Yutang in From Pagan to Christian (1959), p. 85
The Doctrine of the Mean

Source: Intercourse (1987), Chapter 8