And He saith unto them, Follow Me, and I will make you fishers of men. And they straightway left their nets, and followed Him. And going on from thence, He saw other two brethren, James the son of Zebedee, and John his brother, in a ship with Zebedee their father, mending their nets; and He called them. And they immediately left the ship and their father, and followed Him. – Matthew 4:19-22

These men were to leave their pursuits; they were to leave their companions; they were, in fact, to quit the world, that their one business might be, in their Master’s name, to be fishers of men. We are not all called to leave our daily business, or to quit our families. That might be rather running away from the fishery than working at it in God’s name. But we are called most distinctly to come out from among the ungodly, and to be separate, and not to touch the unclean thing. We cannot be fishers of men if we remain among men in the same element with them. Fish will not be fishers. The sinner will not convert the sinner. The ungodly man will not convert the ungodly man; and, what is more to the point, the worldly Christian will not convert the world.

Brethren, the use of the church in the world is that it should be like salt in the midst of putrefaction; but if the salt has lost its savor, what is the good of it? If it were possible for salt itself to putrefy, it could but be an increase and a heightening of the general putridity. The worst day the world ever saw was when the sons of God were joined with the daughters of men. Then came the flood; for the only barrier against a flood of vengeance on this world is the separation of the saint from the sinner. Your duty as a Christian is to stand fast in your own place and stand out for God, hating even the garment spotted by the flesh, resolving like one of old that, let others do as they will, as for you and your house, you will serve the Lord.~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1906.cfm