The cross indeed has central place. It is the symbol of our salvation. The message of the cross foolishness to those who are perishing, wrote St. Paul, but to those who are being saved it is the power of God (1Cor 1:18). I used this passage the other night at our youth group while making ice cream. Making ice cream is actually somewhat counter intuitive. Most of the kids present kept thinking that the ice surrounding the ice cream dasher was cooling and ultimately freezing the creamy mixture within. Not so. The cold of the ice does not flow in. If that were so, we would not need the salt. So as we made the ice cream, I explained how it all worked, and that the key was to know that ice and salt need energy to enter in so that they can react. The energy in this case comes from the heat stored in the creamy liquid. The whole idea of making ice cream is to pump heat out. Cold doesn't exist, technically speaking. Energy in the form of heat flows out. Ice cream, made this way, does not go the way we think it might. God's work of redemption, rescuing his chosen people, does not go the way we think. God does not send the Son to come and conquer. Rather God sends the Son to come and die, defeating the enemies of sin, death and the devil.
The cross marks and shapes our lives. We mark it on the newly baptized as the reminder that we are bound to the one who died on the cross so that we might live by it. The Feast of the Holy Cross is a good day to remember that our lives are to be cruciform. Luther picks this up in his treatise On the Councils and the Church, where he lists the "Possession of the Holy Cross" as the seventh mark of the church. Just as with the first "Possession of the Word of God," the mark does not mean the simple possession of the physical thing. The possession of the Word of God means the Word proclaimed. The possession of the Holy Cross means people whose lives show the reality of the cross. Luther writes,
Seventh, the holy Christian people are externally recognized by the holy possession of the sacred cross. They must endure every misfortune and persecution, all kinds of trials and evil from the devil, the world, and the flesh (as the Lord’s Prayer indicates) by inward sadness, timidity, fear, outward poverty, contempt, illness, and weakness, in order to become like their head, Christ. And the only reason they must suffer is that they steadfastly adhere to Christ and God’s word, enduring this for the sake of Christ, Matthew 5 [:11], “Blessed are you when men persecute you on my account.” They must be pious, quiet, obedient, and prepared to serve the government and everybody with life and goods, doing no one any harm. ...The Feast of the Holy Cross is the day to ponder the sacrifice of Christ, how it is so counter intuitive, and yet how its good news shapes and forms our lives.
But when you are condemned, cursed, reviled, slandered, and plagued because of Christ, you are sanctified. It mortifies the old Adam and teaches him patience, humility, gentleness, praise and thanks, and good cheer in suffering. That is what it means to be sanctified by the Holy Spirit and to be renewed to a new life in Christ; in that way we learn to believe in God, to trust him, to love him, and to place our hope in him, as Romans 5 [:1–5] says, “Suffering produces hope,” etc.