Was... ? Figure of speech Erotesis. Rightly supplied in following clauses.
Thou didst ride. Reference to Pentateuch (Deuteronomy 33:26; Deuteronomy 33:27).
horses. horses [of power].
and. Some codices, with three early printed editions (one Rabbinic), Septuagint, Syriac, and Vulgate, read this "and" in the text.