Abraham has become sufficiently wealthy and powerful for Abimelech and his chief captain to make a journey specifically to see him. He is still living in the land of the Philistines (Genesis 21:34) by permission of the king (Genesis 20:15).
It is a right and proper thing for us to take a solemn oath under important circumstances which call for it, and it is no contravention of Christ’s injunction in the Sermon on the Mount, not to swear at all (Matthew 5:34-37).
The Prosperity Gospel teachers use passages like this to argue that Christians should expect to be blessed by God with riches today. But God made a particular covenant with Abraham, and there were two distinct parts to it. One part was temporary and involved promises to his physical descendants. They were to receive physical promises: a land of their own, plentiful harvests, protection from their enemies, and material prosperity. This part of the covenant we could call the national covenant and it was temporary until the time that Christ came. Abraham enjoyed these physical promises also, although many of them were only given to his descendants after he was dead. But he also had a spiritual seed, all who believe, both Jews and Gentiles. They were given far greater spiritual and eternal promises, of which the material promises given to the Jews were only a picture. Abraham, Hebrews tells us, did not set great value on these physical blessings, but saw in them God’s pledge to give him something far more wonderful in the world to come (Hebrews 11:16). Believers today do not inherit these material promises, but expect their good things in heaven. In this life the disciple is ready to lose his life lives for Christ’s sake and for the gospel’s, in order that he may save it (Mark 8:35).