The heart of the Gospel is redemption, and the essence of redemption is the substitutionary sacrifice of Christ. They who preach this truth preach the Gospel in whatever else they may be mistaken; but they who preach not the atonement, whatever else they declare, have missed the soul and substance of the divine message. In these days, I feel bound to go over and over again the elementary truths of the Gospel. In peaceful times, we may feel free to make excursions into interesting districts of truth that lie far afield; but now we must stay at home and guard the hearths and homes of the church by defending the first principles of the faith. In this age, there have risen up in the church itself men who speak perverse things. There be many that trouble us with their philosophies and novel interpretations, whereby they deny the doctrines they profess to teach and undermine the faith they are pledged to maintain. … There are plenty who can fiddle to you the new music. It is for me to have no music at any time but that which is heard in heaven: “Unto Him that loved us, and washed us from our sins in his own blood … to him be glory and dominion for ever and ever!” (Rev 1:5-6).
Charles H. Spurgeon
The Metropolitan Tabernacle, “The Heart of the Gospel,” Sermon text: 2 Corinthians 5:20–21 (1886).