The surge of the Pentecostal movement in this century has brought new relevance to the study of the Spirit of God in the Old Testament. Surprisingly, however, this theme has been largely neglected by Pentecostal scholars. Ma seeks to fill this gap by providing an in-depth study of the spirit of God in the Isaianic traditions. He argues that the Old Testament concept of the Spirit of God has more than one root, and that the development of the various spirit traditions can be fruitfully traced. The study utilizes a synchronic approach together with historical analyses in order to elucidate the message of the book of Isaiah. The author concludes that the concept of the Spirit of God retains a strong eschatological significance throughout the book.