Charles Spurgeon
The heart of the gospel is redemption, and the essence of redemption is the substitutionary sacrifice of Christ.

Poor souls are apt to think that all those whom they read or hear of to be gone to heaven, went there because they were so good and holy. Yet not one of them, not any one that is now in heaven (Jesus Christ alone excepted), did ever come there any other way but by forgiveness of sins.
John Owen