The Holy Spirit is not in the text, obviously, but some commentaries that suggest the restrainer is the Spirit. He is not, that is just guess work. The answer is in the text ,in verse three. Do you see it? You will find truth in the Word. Commentaries are filled with "some scholars believe, could be, might be, some others think, etc. Only the word is truth, and that if righty divided. Let's hear some real answers, and stick to the question asked.