משך חכמה — פינחס... הנני נותן לו את בריתי שלום

Q — The Midrash says "בדין הוא שיטול שכרו" — why was it questionable in the first place that Pinchas should receive reward?

A — Two categories of mitzvot: (1) acts of removing evil (vengeance, קנאות) — their reward is reserved for עולם הבא, since "לא עשה טוב בעולם המעשה"; (2) acts of chesed and good — their fruits are enjoyed in olam hazeh too. Pinchas's act, on its face, belonged to category (1). But it also had a chesed dimension — by halting the מגפה and arguing for Israel before Hashem ("דן את חברו לכף זכות," Sanhedrin 44a), he saved 24,000 lives, which puts it in category (2) — earning a permanent ברית שלום already in this world.