build on sand
Use an unstable foundation, as in If you buy nothing but high-risk stocks, your portfolio will be built on sand. This metaphor appears in the New Testament, where Jesus likens those who do not heed his sayings to a foolish man who builds his house on sand, which then is washed away by rain, flood, and wind (Matthew 7:24–27). [c. 1600]
Words nearby build on sand
build,
build down,
build in,
build into,
build on,
build on sand,
build up,
build-down,
buildable,
builder,
builder's knot