"Solid Rock" in the Bible: Matthew 7:24-25
There are few things stronger than rock. The right kind of solid rock can withstand great pressure and serve as a foundation or building block for great buildings and structures. In the parable of the wise and foolish builders, Jesus says that the wise builder builds upon a foundation of rock, the foolish on a foundation of sand.
http://biblegateway.com/passage/?search=Matt.7.24-Matt.7.25&version=NIV