Midrash for Chullin 120:57

עוים שכל הרואה אותם אוחזתו עוית

the Holy One, blessed be He, said: Let the Kaphtorim come and take away the land from the Avvim, who are philistines, and then Israel may come and take it away from the Kaphtorim.<span class="x" onmousemove="('comment',' The Israelites, being bound by the oath of Abraham not to molest the Philistines, indirectly, however, gained possession of their land by dispossessing the Kaphtorim who had vanquished the Philistines.');">²⁴</span>

Sifrei Devarim