Adam Clarke on Psalms 132:3

Surely I will not come - This must refer to the situation of the temple; or, as we would express it, he would not pass another day till he had found out the ground on which to build the temple, and projected the plan, and devised ways and means to execute it. And we find that he would have acted in all things according to his oath and vow, had God permitted him. But even after the Lord told him that Solomon, not he, should build the house he still continued to show his good will by collecting treasure and materials for the building, all the rest of his life.