Rashi on Deuteronomy 19:8/רש"י על דברים י״ט:ח׳

1ואם ירחיב … כאשר נשבע AND IF [THE LORD THY GOD] ENLARGE [THY TERRITORY], AS HE HATH SWORN [UNTO THY FATHERS] to give thee the land of the Kenite, the Kenizzite and the Kadmonite (Sifrei Devarim 184:3).