Moses took the bones of Joseph with him because Joseph had made the sons of Israel swear an oath. He had said, “God will surely come to your aid, and then you must carry my bones up with you from this place.” (Exodus 13:19 NIV84)
I would imagine after 430 years, that to the average Israelite, names like Abraham, Isaac, Jacob and Joseph were almost mythical. Why mythical? Well, because they had been enslaved by the Egyptians most of their time in Egypt, and any thought of a gracious God bringing them to a promised land seemed far reaching…maybe even impossible. But regardless of the improbability of their ever being set free from their slavery, an oral tradition carried throughout the 430 years that when (not if) God comes to their aid, they were to take Joseph’s bones with them as they left Egypt. And take out his bones they did! The Lord was faithful to His promise to Abraham, Isaac and Jacob, and the Israelites left Egypt as free people with the bones of their patriarch Joseph.
Oaths like Joseph’s, made in connection to the promises of God are certain to be fulfilled. God is always faithful to His promises. So go ahead, make some oaths about your salvation or your eternal destiny and know that you are safe. Those oaths are as certain as the promises they are rooted in. But one more thing–know that God fulfills His promises according to His will and perfect timing. When Joseph forced the leaders of Israel to take the oath about his bone, I’m certain he didn’t think it would take 430 years. Know that God may not work in your timeframe, but be certain He will work.