John Trapp on Isaiah 43:3

Ver. 3. I gave Egypt for thy ranſom] quaſi victimam piacularem à Sennacheribo mactandam loco Judaeae, in exchange for thee; ſo the Septuagint render it: This was done when Tirhakah King of Egypt and Ethiopia was beaten by Sennacherib, who was then making toward Jeruſalem, which he had already devoured in his hopes, chap. 37.9. Thus the righteous is delivered out of trouble, and the wicked cometh in his ſtead, Prov. 11.8. Saul and his people were afflicted by the Philiſtins that David might eſcape, 1 Sam. 23. The Canaanites were rooted out, to make room for the Iſraelites. Charles the fifth, and Francis the French King, after a mutual agreement to root out Lutheraniſme, fall together by the eares, and the Church the while hath her Halcyons. So the Turks and Perſians are at deadly feud, to the great ſafeguard of Chriſtendom: and the Popiſh party are as a bulwark betwixt thoſe Mahometans, and the Proteſtants.