And the LORD was with Joseph, and he was a prosperous man; and he was in the house of his master the Egyptian. Genesis 39:2
When Joseph, the son of Jacob was sold to Egypt by his brothers, he worked as a slave in the house of an Egyptian named Potiphar. However, contrary to the expectations on "slaves" by most people, Joseph was described as "prosperous" in the Bible!
So, how can a slave be prosperous?
Natural and Spiritual Realm
The Bible often compares the natural and the spiritual realm. Prosperity in the Natural Realm means eating and drinking, and all kinds of physical pleasures; but Prosperity in the Spiritual Realm on the other hand, is righteousness, peace and joy in the Holy Spirit.
For the kingdom of God is not eating and drinking; but righteousness, and peace, and joy in the Holy Spirit. Romans 14:17
So obviously, even though Joseph was working as a slave, he must be full of righteousness, peace, and joy in the Holy Spirit!
Which One Should We Choose?
The Bible has told us many times that the physical world we now experience is short lived, but the spiritual realm is eternal. Which one a person chooses often indicates how much he believes in the Word of the Lord.
While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal. 2 Corinthians 4:18
In the story of Lazarus (Luke 16:19-31), the rich man who devoted all his time and energy in building wealth ends up in eternal torment. On the other hand, poor beggar Lazarus was carried by the angels to receive eternal bliss.
In many aspects, these two realms work almost opposite to each other. If one values spiritual prosperity, he will probably be unwilling to lie, cheat, or do anything that disturbs his inner peace even though that might bring him some kind of physical reward or comfort.
A Church in Poverty But Yet Prosperous
In the Book of Revelation, we see another Church which is like Joseph. Even though they are in physical poverty, they are rich in God's eyes, and their reward is a crown of (eternal) life.
And unto the angel of the church in Smyrna write ..... I know your works, and tribulation, and poverty, (but you art rich) ..... be faithful unto death, and I will give you a crown of life ..... He that overcomes shall not be hurt of the second death. Revelation 2:8-11