Ruth 1:17
Where thou diest, will I die, and there will I be buried: the LORD do so to me, and more also, if ought but death part thee and me. Where thou diest, will I die, and there will I be buried: the LORD do so to me, and more also, if ought but death part thee and me.
In this vow Ruth the Moabitess turns away from idolatry to the worship of the true God. By that turning she unites herself with His chosen people. Her choice shows that outsiders who forsook false worship were to become part of Israel.
Her decision is an example of God's purpose that the revelation of His character through Israel would draw men of all nations to Him. It proves that the gospel invitation was for all the world. That ingathering was to increase Israel in numbers and enlarge its borders until its kingdom embraced the world.