An unfavorable soil for the growth of piety

(Archibald Alexander, "The spiritual warfare")

Worldly prosperity has ever been found to be an
unfavorable soil for the growth of piety. It . . .
  blinds the mind to spiritual and eternal things,
  dries up the spirit of prayer,
  fosters pride and ambition,
  furnishes the appropriate food to covetousness,
  leads to a sinful conformity to the spirit, maxims,
     and fashions of the world.

Very few have been enabled to pass this 'ordeal' without
serious injury, and have come forth like the three children
from Nebuchadnezzar's furnace--without the smell of fire
on their garments; but this could not have been unless
the Son of Man had been with them! Such people use
all their health, influence, and wealth in promoting the
kingdom of Christ.

But generally, God in mercy refuses to give worldly
prosperity to His children. He has "chosen the poor
of this world, to be rich in faith"--that is, He has
commonly chosen poverty as the safest condition
for His children. His are "an afflicted and poor people
--who trust in the name of the Lord." Zephaniah 3:12

"For the love of money is a root of all kinds of evil, and
 by craving it, some have wandered away from the faith
 and pierced themselves with many pains. Now you,
 man of God, run from these things; but pursue
 righteousness, godliness, faith, love, endurance, and
 gentleness." 1 Timothy 6:10-11