Before thy wickedness was discovered, as at the time of thy reproach of the daughters of Syria, and all that are round about her, the daughters of the Philistines, which despise thee round about.
Before thy wickedness was discovered - manifested to all, namely, by the punishment inflicted on thee.
As at the time of thy reproach of ... Syria, and ... the Philistines - the indignity and injuries done thee by Syria and the Philistines in the reign of Ahaz (2 Kings 16:5; 2 Chronicles 28:18; Isaiah 9:11-12).