quarried stones can't lift themselves

I'm quoting this from memory - something I heard this evening and have to write down before I forget.

In a sermon on Mark 13:34-37, Robert Murray McCheyne talks about Christ as the Builder of his house, the Church, and (possibly with a reference to the verse about 'living stones' in Peter, although I don't remember that specifically) he said that Christians before they were converted were firmly embedded in the quarry of the world. It took the power of the Holy Spirit to dig them out of that quarry. But then, he said, even stones that have been quarried are completely unable to move themselves - they need to be lifted and carried by the Builder, and the Builder places them exactly where they should be.

(In case you're wondering how stones and buildings come into Mark 13:34-37, this was just a passing comment under the point that in this parable the Church on earth is said to be like a house, and Christ is the master of the house - the foundation of it and also the builder of it.)