The contrast between solid rock and shifting sand is found in Bible and Hymnal. The irony found in the analogy linking Christ and things spiritual to the "rock," and things transient and worldly, tangible, to "shifting sand" is not lost with the events of this week. So is the impulse to return to Egypt after one has been freed from its bondage.

Matthew 7:24 Therefore whosoever heareth these sayings of mine, and doeth them, I will liken him unto a wise man, which built his house upon a rock: Matthew 7:25 And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell not: for it was founded upon a rock.

Luke 14:28 For which of you, intending to build a tower, sitteth not down first, and counteth the cost, whether he have sufficient to finish it? Luke 14:29 Lest haply, after he hath laid the foundation, and is not able to finish it, all that behold it begin to mock him, Luke 14:30 Saying, This man began to build, and was not able to finish.