To rest is to lean upon something. Is it not? So spiritually. We want to lean upon something. The Lord himself has given us this figure. "Who is this that cometh up from the wilderness, leaning upon her Beloved?" The figure of "a rock" on which the Church is built, "the foundation" which God has laid in Zion, points to the same idea, that of leaning or dependence.
Now when the soul comes to lean upon Jesus, and depend wholly and solely on him, it enters into the sweetness of the invitation. Have we not leant upon a thousand things? And what have they proved? Broken reeds that have run into our hands, and pierced us. Our own strength and resolutions, the world and the church, sinners and saints, friends and enemies, have they not all proved, more or less, broken reeds? The more we have leant upon them, like a man leaning upon a sword, the more have they pierced our souls. The Lord himself has to wean us from the world, from friends, from enemies, from self, in order to bring us to lean upon himself; and every prop he will remove, sooner or later, that we may lean wholly and solely upon his Person, love, blood, and righteousness.
But there is another idea in the word "rest"—termination. When we are walking, running, or in any way moving, we are still going onwards; we have not got to the termination of our journey. But when we come to the termination of that we have been doing, we rest. So spiritually. As long as we are engaged in setting up our own righteousness, in labouring under the law, there is no termination of our labours. But when we come to the glorious Person of the Son of God, when we hang upon his atoning blood, dying love, and glorious righteousness, and feel them sweet, precious, and suitable, then there is rest. "We which have believed do enter into rest," says the Apostle. His legal labours are all terminated. His hopes and expectations flow unto, and centre in Jesus—there they end, there they terminate; such a termination as a river finds in the boundless ocean.