“And God divided the light from the darkness.” (Genesis 1:4)
A believer has two principles at work within him. In his natural estate he was subject to one principle only, which was darkness; now light has entered, and the two principles disagree. Mark the apostle Paul’s words in the seventh chapter of Romans: “I find then a law, that, when I would do good, evil is present with me. For I delight in the law of God after the inward man: but I see another law in my members, warring against the law of my mind and bringing me into captivity to the law of sin, which is in my members.”
How is this state of things occasioned?
“The Lord divided the light from the darkness.” Darkness, by itself, is quiet and undisturbed, but when the Lord sends in light, there is a conflict for the one is in opposition to the other: a conflict which will never cease till the believe is altogether light in the Lord. If there be a division within the individual Christian, there is certain to be a division without. So soon as the Lord gives to any man light, he proceeds to separate himself from the darkness around; he secedes from a merely worldly religion of outward ceremonial, for nothing short of the gospel of Christ will now satisfy him, and he withdraws himself from worldly society and frivolous amusements, and seeks the company of the saints, for “We know we have passed from death unto life, because we love the brethren.”
The light gathers to itself, and the darkness to itself. What God has divided, let us never try to unite, but as Christ went [outside/away from] the camp, bearing His reproach, so let us come out from the ungodly, and be a peculiar people. He was holy, harmless, undefiled, separate from sinners; and, as He was, so we are to be nonconformists to the world, dissenting from all sin, and distinguished from the rest of mankind by our likeness to our Master.
~ C.H. Spurgeon (from Morning and Evening, a daily devotional; paragraphing added)