Surely, if I sent thee to them, etc. The "surely" represents the Hebrew "if not" taken as a strong affirmation, just as "if" in Psalms 95:11 represents a strong negation; compare the use of the fuller formula jurandi in 1 Samuel 3:17; 2 Samuel 3:35; 2 Samuel 19:13; and of the same in Deuteronomy 1:35; Isaiah 62:8; and in Ezekiel himself (Ezekiel 17:19).
The margin of the Authorized Version, If I had sent thee to them, would they not have hearkened, etc.? expresses the same meaning, but is less tenable as a translation. The thought in either case finds its analogue in our Lord's reference to Sodom and Gomorrah, to Tyre and Sidon (Matthew 11:21-24; Luke 10:12-14).
Israel was more hardened than the worst of the nations round her.