Be Thoroughly Tested

Luther on Isaiah 28:16:

...Christ is a tested stone, that is, distressed and afflicted, or He is a testing stone, that is, a stone by whose shape all other stones are tested, so that we may be conformed to the image of the Son of God (Rom. 8:29). As Christ was polished, hewn, and squared by the promise, by death and the cross, so we, in His image, should become well polished by such suffering and such a cross. Therefore it behooves all the godly to be thoroughly tested by cross and persecution. For this reason the flesh which shrinks from the cross remains unpolished in its desires and unsuited to this stone.

Martin Luther, Luther's Works, ed. Jaroslav Pelikan and Helmut Lehmann. vol. 16, CD-ROM (Saint Louis: CPH, 1999).