A.T. Robertson Commentary Revelation 1:15

"and his feet like unto burnished brass, as if it had been refined in a furnace; and his voice as the voice of many waters." — Revelation 1:15 (ASV)

Burnished brass (χαλκολιβανω). Associative-instrumental case after ομοιο. This word has so far been found nowhere else save here and 2:18. Suidas defines it as an ηλεχκτρον (amber) or a compound of copper and gold and silver (aurichalcum in the Latin Vulgate). It is in reality an unknown metal.

As if it had been refined (ως πεπυρομενης). Perfect passive participle of πυροω, old verb, to set on fire, to glow, as in Eph 6:16; Revelation 3:18. The feminine gender shows that η χαλκολιβανος is referred to with της χαλκολιβανου understood, for it does not agree in case with the associative-instrumental χαλκολιβανω just before. Some would call it a slip for πεπυρομενω as Aleph, and some cursives have it (taking χαλκολιβανω to be neuter, not feminine). But P Q read πεπυρωμενο (masculine plural), a correction, making it agree in number and gender with ποδες (feet).

In a furnace (εν καμινω). Old word, in N.T. also 9:2; Matthew 13:42,50.

As the voice of many waters (ως φωνη υδατων πολλων). So the voice of God in the Hebrew (not the LXX) of Eze 43:2. Repeated in 14:2; 19:6.