John Wesley on Isaiah 27:1

Leviathan - By this leviathan, serpent and dragon (for all signify the same thing) be understands some powerful enemy or enemies of God, and of his church or people, which may well be called by these names, partly for their great might, and partly for the great terror and destruction which they cause upon the earth. The piercing - Which by its sting pierces deeply into mens bodies. Crooked serpent - Winding and turning itself with great variety and dexterity. Whereby he seems to signify the craftiness and activity of this enemy, whose strength makes it more formidable.