אברהם אבינו עשה יצר הרע טוב (ברכות ט:ב)
Abraham our forefather turned his evil inclination into good
אברהם אבינו עשה יצר הרע טוב דכתיב ומצאת את לבבו נאמן לפניך (נחמיה ט:ח).
אמר רבי אחא והפסיד?
אלא וכרות עמו הברית (והחסד) (שם).
אבל דוד לא היה יכול לעמוד בו והרגו בלבבו.
(מאי טעמא ולבי חלל בקרבי” (תהילים קט:כב) (ברכות ט:ה סז,ב
Abraham our Patriarch had the ability to discipline his evil inclination so that it manifests in good. Abraham had dominion over it and could steer it in the direction that he wished. In essence he had two good inclinations as hinted in the two beths of לבבו.
David did not have such dominion over his evil inclination and was forced to subdue it, either by putting his body through infliction or some other means. This is hinted in the single beth of לבי which suggest that he only had one good inclination.
The very specific usage of the terms “kill” and “empty” (חלל reminiscent of “corpse”) in reference to David may be symbolic of his military role.
The assumption here is that a disciplined evil inclination is in fact a good inclination. But to what extent are the two the same? This is precisely Rabbi Aha’s question. Did Abraham no longer receive reward for abstaining from sin ? Does one not receive reward for virtue?
The Scripture teaches us that even one who does not need to apply restraint from impulses of sin still receives reward for abstaining. This is the treaty that God made with Abraham.