pennies from heaven
Unexpected good fortune, a windfall, as in They sent back our check—pennies from heaven. This expression may have originated with a song and motion picture so named (1936), popularized by Bing Crosby.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.