God is caring for man mainly to make man holy. To be holy means to be separated unto God. Man's fall caused him to depart from God to become common, worldly, secular, and even dirty. So God needs to take care of man, making man separate from all things other than Himself. This is to make man holy. Thus, the Spirit in the Old Testament is the Spirit of holiness in God's making His chosen people holy unto Himself (Psa. 51:11; Isa. 63:10-11). This is not the same as the Holy Spirit, which is used in the New Testament. The Holy Spirit is more intensified than the Spirit of holiness.
Now we come to the New Testament. In the New Testament, the revelation concerning the Spirit is more complicated.
The first divine title used for the Spirit in the New Testament is the Holy Spirit. According to the Greek text, the title translated as the Holy Spirit may be in two forms: the Spirit the Holy or the Holy Spirit. According to my understanding, this means that in the New Testament age, the very God who is the Spirit is "the Holy." God is a Spirit and this Spirit now is totally "the Holy." We are now in an age in which God Himself as the Spirit is "the Holy" to make man not only separated unto Him but also one with Him. In the Old Testament, the most God could do with man was to make man separated unto Him but not one with Him. But now in the New Testament age, the time has come in which God would go further and deeper to make man absolutely one with Him, to make man Him and to make Him man. Athanasius, who was one of the church fathers, said concerning Christ: "He was made man that we might be made God." This means that we are made God in life and in nature, but not in the Godhead. This process takes place by the Spirit the Holy.
In the New Testament, two divine titles of the Spirit are very striking: the first one and the last one. The first one is the Spirit the Holy and the last one is the seven Spirits (Rev. 1:4; 4:5; 5:6). The Spirit the Holy is for making man God, making man one with God and making God one with man. In other words, the New Testament age is for bringing God and man together, to constitute them together so that they coinhere (mutually indwell each other) to be one spirit (1 Cor. 6:17). Man and God become one spirit, one entity. Eventually, the Spirit the Holy has to be seven times intensified to become the seven eyes of the Lamb. All the living creatures were made by God with two eyes, but eventually the Lamb will have seven eyes, and these seven eyes are the seven Spirits of God, the sevenfold-intensified Spirit.