I don’t know if my friend Pr. Krenz over at Cruce Tectum had Hermann Sasse in mind when he came up with his title, but here are some words he could have had in mind:
In this world of sin and death there exists God’s holy people, the congregation of saints, Christ’s kingdom in which He reigns through the inconspicuous means of grace, forgiving sins, redeeming from eternal death. This kingdom is cruce tectum [under the cross] until at the end of the world with the glory of Christ also the glory of His church will be revealed. This doctrine of the ecclesia abscondita [hidden church] is not a Lutheran invention. Like the doctrine of the justification of the sinner, like the Lutheran doctrine of the sacraments, and like the entire theologia crucis [theology of the cross] of our Reformers, it is a rediscovery of the eschatology of the New Testament: “Beloved, now are we the sons of God, and it doth not yet appear what we shall be” (1 John 3:2)….
The church as the spiritual or mystical body of Christ exists wherever members of this body are, but it exists in the smallest local church, just as the sacramental body of Christ is in its entirety in, with, and under each consecrated host and in each particle of the host. And just as the sacramental body of Christ remains unbroken, undivided, so the spiritual body remains one….
This, then, would be the pre-eminent task of the Lutheran Church in view of the present Ecumenical Movement, to testify to the Biblical doctrine of the church…. It is wrong to conclude from the reluctance of Lutherans to co-operate in certain ecumenical organizations of our time that our church is not interested in the outward unity of the children of God and does not feel its ecumenical obligation. On the contrary, no church has a broader ecumenical outlook than the Church of the Augsburg Confession…. In an age when large parts of Christendom have lost the Biblical distinction between truth and error, church and heresy, and have lost or are in danger of losing, with this distinction, the pure Gospel and the sacraments of Christ, the means of grace by which the church lives, it is the highest ecumenical duty to call all Christians back to the truth of the Gospel–all Christians, including ourselves. In deep humility only, always aware of our own shortcomings, of the weakness of our faith, our lack of love, our failure to confess where we ought to have confessed, in deep repentance of our manifold sins and with continuous prayer that God may keep us steadfast in His Word can we and must we ask our fellow Christians to submit with us to the Word that, as it maintains and saves the church, judges us all….
More martyrs have died in this century than in all previous centuries of the church. It was the way of the cross the church had to go. But this is the way of the church at all times, the church of the crucified and risen Lord. Cruce tectum, hidden under the cross, is His Kingdom in this world, until with His advent in glory, the hidden glory and unity of His body, the church, will be revealed.
[Hermann Sasse, “The Ecumenical Movement,” Concordia Theological Monthly, XXXI:2 (February 1960)]