Through the tender mercy of our God - the sole spring, necessarily, of all salvation for sinners.
dayspring from on high - either Christ Himself, as the “Sun of righteousness” (Mal 4:2), arising on a dark world [Beza, Grotius, Calvin, Deuteronomy Wette, Olshausen, etc.], or the light which He sheds. The sense, of course, is one.