Musar על בבא בתרא 150:2

This is what G–d meant when He said to Israel: והייתם לי סגולה מכל העמים. "You will be precious to Me more than any of the other nations" This meant that any favours that the nations would experience, Israel would also experience. When G–d continued: ואתם תהיו לי ממלכת כהנים וגוי קדוש, He announced that what Israel would receive as a part of the bounty G–d shares out to the Gentiles would not be considered as of value since Israel are a kingdom of priests. All Israelites are considered as princes, sons of kings. The word "kings" refers to the kingdom of Heaven. When the Torah says of Israel "you are a holy nation," the word "holy" is to be understood as similar to what the sages say about the angels paying their respects to the righteous in the world of the future by addressing them as קדוש, "holy."