Either,
1. In giving me that support and assurance of his favour which for the present I enjoy. Or,
2. In giving me that mercy which he hath freely promised me; it being a common thing for David and other prophets to speak of future deliverances as if they were already come, that so they may signify both the infallible certainty of the thing, and their firm assurance thereof. But the words may be rendered, when he shall have dealt bountifully with me. This verb properly signifies to requite, or reward, (as it may be taken here, for there is a reward of grace as well as of debt, Romans 4:4) but here it signifies a free and bountiful giving, as it doth also Psalms 119:17, Psalms 142:7.