Not a little confusion exists today over the work of the Holy Spirit in the Old Testament dispensation, contrasted with the New. Below is B. B. Warfield's excellent summary of the matter:
The old dispensation was a preparatory one and must be strictly conceived as such. what spiritual blessings came to it were by was of prelibation. They were many and various. The Spirited worked in providence no less universally then than now. He abode in the Church not less really then than now. He wrought in the hearts of God's people not less prevalently than now.
All the good that was in the world was then as now due to him. All the hope of God's Church then as now depended on him. Every grace of the godly life then as now was a fruit of his working. But the object of the whole dispensation was only to prepare for the outpouring of the Spirit upon all flesh. He kept the remnant safe and pure, but it was in order that the seed might be preserved. This was the end of his activity then.
The dispensation of the Spirit, properly so called, did not dawn, however, until the period of preparation was over and the day of outpouring had come.
The mustard seed had been preserved through all the ages only by the Spirit's brooding care. Now it is planted, and it is by his operation that it is growing up into a great tree which shades the whole earth, and to the branches of which all the fowls of heaven come for shelter.
It is not that the work is more real in the new dispensation than in the old. It is not merely that it is more universal. It is that it is directed to a different end--that it is no longer for the mere preserving of the seed unto the day of planting, but for the perfecting of the fruitage and the gathering of the harvest.
The Church, to use a figure of Isaiah's, was then like a pent-in stream; it is now like that pent-in stream with barriers broken down and the Spirit of the Lord driving it. It was he who preserved it in being when it was pent-in. It is he who is now driving on its gathered floods till it shall cover the earth as the waters cover the sea. In one word, that was a day in which the Spirit restrained his power. Not the great day of the Spirit has come.
B. B. Warfield, "The Spirit of God in the Old Testament," Selected Shorter Writings, edited by John E Meeter (Nutley, New Jersey: Presbyterian and Reformed Publishing Company, 1973) 2: 716f.