The Cross of Christ, A.W. Tozer

The cross of Christ is the most revolutionary thing ever to appear among men. The cross of old Roman times knew no compromise; it never made concessions. It won all its arguments by killing its opponent and silencing him for good. It spared not Christ, but slew Him the same as the rest. He was alive when they hung Him on that cross and completely dead when they took Him down 6 hours later. That was the cross the first time it appeared in Christian history.

The radical message of the cross transformed Saul of Tarsus and changed him from a persecutor of Christians to a tender believer and an apostle of the faith. Its power changed bad men into good ones. It shook off the long bondage of paganism and altered completely the whole moral and mental outlook of the Western world. 

All this it did and continued to do as long as it was permitted to remain what it had been originally--a cross. Its power departed when it was changed from a thing of death to a thing of beauty. When men made of it a symbol, hung it around their necks as an ornament or made its outline before their faces as a sign [to ward off evil], then it became at best a weak emblem, at worst a positive fetish. As such it is revered today by millions who know absolutely nothing about its power.