If Christians do not cultivate unity in doctrine and in life among themselves, they are misled by their flesh and blood, standing by peacefully as divisions arise and discord grows day by day. God did not give His gifts to only one Christian or to one Christian congregation. Instead, He distributes them in such a way that all must work together to succeed. When divisions surface, success is hindered—errors increase, quarrels become more passionate, confusion grows, false judgments and a spirit of condemnation ensue, and sects become more numerous. When this happens, how many lose the foundation upon which their faith is built! When the poor world sees how disunited Christians are among themselves, it finds little reason to embrace the faith and is even comforted in rejecting it. Many are offended who might have been won to Christianity.
Christian unity always produces a blessing. If the Church is one in doctrine and life, in faith and love, it shares its gifts and knowledge. It then grows in the wealth of knowledge, the power of faith, the fervor of love, the comfort of the Holy Ghost, and the liveliness of hope. It grounds itself ever more deeply and builds itself ever more gloriously, adorned with all sorts of gifts of the Spirit. It then extends its hands to raise up shepherds and soldiers who pursue the work of converting those who sit in darkness and in the shadow of death and who struggle against the enemies of the truth.
Satan knows all too well what kind of power the Church exercises when it is united. It then not only greens and bears fruit, but it also stands invincible against all of its enemies, conquering them and extending its borders. Therefore, Satan’s most important and dangerous strategy, which he employs to damage the Church is destroying its unity and sowing discord among its members. And how easily he succeeds! how quickly is the holy bond that binds Christians together torn apart! how quickly an ember of discord among the ashes is fanned into a bright flame that seizes and lays waste entire congregations! How necessary it is, then, that the Church carefully cultivate unity, pursuing it as a precious jewel!
– C.F.W. Walther