When did God's people first have to be separated from the world?

God's people first had to be separated from the world from day one. God could not deal with Abraham while he was in Ur among pagan relatives, so separation was required before God could work with him. Later, God separated Goshen from Egypt during the plagues.

Les teaches that separation began with Abraham. God couldn't deal with Abraham in the midst of Ur, among all his pagan relatives who were idolaters and worshipped other gods. So there had to be a separation before God could work with him. Then in Genesis 13, Abram told Lot to separate, and after Lot was separated, the Lord spoke to Abram. Les points out it started with day one—God's people had to be separated from the world around them. Later in Exodus 8:22-23, God said He would sever or separate the land of Goshen where His people dwell, so that no swarms of flies would be there, to show He is the Lord in the midst of the earth. In the first three plagues Israel had to come under them as well as the Egyptians, but then God made a separation.

When did God start requiring His people to be separate from the world?

God began requiring separation from the world at the very start of His dealings with Abraham. Abraham could not remain in Ur among pagan, idolatrous relatives; separation had to occur before God could work with him. This principle continued, as God later severed Goshen from Egypt during the plagues.