a blessing and a curse

From the King James translation of Deuteronomy 11:26 (“Behold, I set before you this day, a blessing and a curse.”).[1]

• Rhymes: -ɜː(ɹ)s

a blessing and a curse (plural not attested)

1. Something that is both a benefit and a burden, or that may seem initially beneficial but also brings unforeseen negative consequences
   • 1835, The London Riddler; or, The Art of Teasing Made Easy:

     What is that which is a friend and an enemy, a blessing and a curse, which saves life and takes it away; is long and short, round and square, rough and smooth, straight and crooked, hard and soft, hot and cold, and most wanted when it is in greatest plenty; which accommodates itself to all palates; is sweet and of bad smell, strong and weak; sometimes able to bear great burdens, but at other times will not bear a pin.

   • 1940, Olive G. Gibson, The Isle of a Hundred Harbors, B. Humphries, Incorporated, page 204:

     On the whole the Contrabando was both a blessing and a curse; it was a blessing and a great benefit in that it brought the necessities of life to the people, but a curse in that it was training them in intrigue, because the contrabandistas often resorted to piracy along the sequestered coasts and on the open seas; they would sell their commodities to the people, then turn around and loot the cattle and hogs in the fields.

• double-edged sword
• a boon and a bane