I suspect because the word for heaven (OURANOS) often (but not always)
occurs in the plural, possibly reflecting the Hebrew HASHAMAIM. Years ago
Adolf Schlatter argued that in Josephus heaven in the plural was used for
the heavens as the place where God is (i.e. the antonym to the earth),
while in the singular it is the counterpart of earth, the two making up the
totality of creation. Note the variation in number in the address to God
and the third petition in the Lord's Prayer in Matt 6.
Edgar Krentz, New Testament
emkrentz@mcs.com OR ***** ekrentz@lstc.edu
Lutheran School of Theology at Chicago
1100 East 55th Street
CHICAGO IL 60615
TEL.: 773-256-0752 FAX: 773-256-0782