Widely regarded as a homily from the Bible, especially in the late 19th and early 20th centuries, this phrase basically states the flip side of the Golden Rule: a more modern version might be “what goes around, comes around.” Though it never appears in the Bible in precisely this form, the concept turns up several times using the key agricultural metaphor of sowing and reaping, from Job 4:8 (“…they that plow iniquity, and sow wickedness, reap the same”) in the Old Testament, to Galations 6:7 (“…whatsoever a man soweth, that shall he also reap”) in the New.
The notion was not confined to ancient Christian texts or lands, however. The great Roman orator and senator Marcus Tullius Cicero (106-43 BCE) also wrote “As you have sown so shall you reap.” Nevertheless, people in recent times have typically regarded it as a Biblical homily, and it turns up in the writings or public statements of theologians and activists as varied as early 20th-century psychic Edgar Cayce and anti-Iraq War protestor Malachi Ritscher, a musician who committed suicide by self-immolation in 2006 as a protest against the war.
In 1935, mixed race Harlem bookmaker Stephanie St. Clair, who had been pressured by mob boss Dutch Schultz to pay him protection money and resisted, made national headlines when she sent a telegram to him at his hospital deathbed that read “As ye sow, so shall ye reap,” even though she had had nothing to do with his assassination by the Mafia.
References to the phrase have turned up in many other contexts, typically with a connotation of Biblical vengeance, from the 1914 silent film “As Ye Sow,” starring Douglas MacLean and Alice Brady, to a 1983 episode of the Home Box Office series “Tales From the Crypt” starring Kyle McLachlan, Patsy Kensit, and Sam Waterston.