Origins
Reward and regard are the same word.βββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ Both descend from a root meaning 'to look back at someone's deeds', but they entered English through different doors. Reward came via Norman French, which preserved the Frankish w. Regard came via Central French, which shifted w to g. The split is a fingerprint of the Norman Conquest.
The deeper root is Proto-Germanic *wardΕnΔ , meaning 'to watch, to guard'. From this single verb English gets ward, warden, guard, guardian, beware, aware, and β through French β reward and regard. All share the core concept of watchfulness.
The original sense of reward was 'to look back at' β to review someone's conduct and respond to it. A reward was the response, the thing you received when someone looked back at what you had done. The shift from 'looking at' to 'paying for' happened naturally: to notice someone's work is the first step toward compensating them.
Later History
The 'wanted' poster reward β money offered for information leading to capture β preserves a legal nuance. It is payment for watchfulness, for guarding the community's interests by looking out for a fugitive.
In modern English, reward has drifted toward the positive. We reward good behaviour but rarely speak of rewarding bad. The neutral 'to regard' still works both ways. But originally, a reward was simply what came back when someone watched.