The first of the three Priestly blessings is, “May Hashem bless you and keep watch/protect you.” (Numbers 6:24)
There is a potential downside to being blessed with material abundance – it can lead to a sense of self-importance and forgetting God. Moses repeatedly warned us of this danger in the book of Deuteronomy (6:10-12, 8:11-14, 32:15).
Our sages taught that there were ten miracles that regularly took place at the Holy Temple in Jerusalem. One was that the rains never extinguished the fire on the woodpile of the altar (Pirkei Avot 5:5). The Hebrew word for rain, geshem, is related to the word for materialism – gashmiyut. Some commentaries spin this idea figuratively to be teaching that for material prosperity to not extinguish the flames of spiritual passion in our service of God takes a miracle!
Therefore, immediately following the prayer that God bless us – the Priests ask that He also ensure that we don’t become corrupted through the abundance we are blessed with.