Rashi on Leviticus 14:34/רש"י על ויקרא י״ד:ל״ד

1ונתתי נגע צרעת [WHEN YOU COME TO THE LAND …]I WILL PUT THE PLAGUE OF THE LEPROSY — This was an announcement to them that these plagues would come upon them (Sifra, Metzora, Section 5 4; Horayot 10a), because the Amorites concealed treasures of gold in the walls of their houses during the whole 40 years the Israelites were in the wilderness (in order that these might not possess them when they conquered Palestine,) and in consequence of the plague they would pull down the house and discover them (Leviticus Rabbah 17:6).