3. was--omitted in the two oldest manuscripts but supported by Vulgate and Coptic.
      to look upon--Greek, "in sight," or "appearance."
      jasper--From Re 21:11, where it is called most precious, which the jasper was not, EBRARD infers it was a diamond. Ordinarily, the jasper is a stone of various wavy colors, somewhat transparent: in Re 21:11 it represents watery crystalline brightness. The sardine, our cornelian, or else a fiery red. As the watery brightness represents God's holiness, so the fiery red His justice executing fiery wrath. The same union of white or watery brightness and fiery redness appears in Re 1:14; 10:1; Eze 1:4; 8:2; Da 7:9.
      rainbow round about the throne--forming a complete circle (type of God's perfection and eternity: not a half circle as the earthly rainbow) surrounding the throne vertically. Its various colors, which combined form one pure solar ray, symbolize the varied aspects of God's providential dealings uniting in one harmonious whole. Here, however, the predominating color among the prismatic colors is green, the most refreshing of colors to look upon, and so symbolizing God's consolatory promises in Christ to His people amidst judgments on His foes. Moreover, the rainbow was the appointed token of God's covenant with all flesh, and His people in particular. Hereby God in type renewed to man the grant originally made to the first Adam. The antitype will be the "new heavens and the new earth" restored to redeemed man, just as the earth, after the destruction by the flood, was restored to Noah. As the rainbow was first reflected on the waters of the world's ruin, and continues to be seen only when a cloud is brought over the earth, so another deluge, namely, of fire, shall precede the new heavens and earth: the Lord, as here, on His throne, whence (Re 4:5) proceed "lightnings and thunderings," shall issue the commission to rid the earth of its oppressors: but then, amidst judgment, when other men's hearts fail them for fear, the believer shall be reassured by the rainbow, the covenant token, round the throne (compare DE BURGH, Exposition of Revelation). The heavenly bow speaks of the shipwreck of the world through sin: it speaks also of calm and sunshine after the storm. The cloud is the regular token of God's and Christ's presence, for example, in the tabernacle's holiest place; on Mount Sinai at the giving of the law; at the ascension (Ac 1:9); at His coming again (Re 4:7).

JFB.