He is perfect in grace. He is perfect in glory. His grace, like himself, is infinite. His glory, like himself, is infinite. You cannot add to or detract from either.
Infinity is like a full well that is overflowing.
When you take away all the outflow, the well is still flowing as fully and as freely as ever. God cannot enrich himself by keeping his grace and glory to himself. He cannot impoverish himself by giving them away. The giving to us of these gifts through his Son, the Lord Jesus Christ, does add a different kind of glory. It adds not an essential glory, but a material glory.