4 ideas
Twenty years earlier the Baghdad merchant Fuwaad ibn Abbas quarreled with his wife Najya and left on a journey without reconciling, and she died while he was away, killed when a wall collapsed. He travels through the gate to the past intending to save her, fails, and arrives too late. He cannot change the event, but understanding it releases him from twenty years of guilt.
Nothing can erase what has been done, and even a gate into the past cannot alter it. What remains possible is repentance, atonement and forgiveness, which change what the past means rather than what happened. Redemption works through understanding and response, never through revision.
The traveler's actions in the past or future were always already part of events, so any attempt to change history turns out to be one of the causes that produced it. Each nested tale shows a visitor's intervention closing a causal loop. The effort to escape an outcome becomes the means of fulfilling it.
Past and future are treated as equally fixed, like two rooms of the same house. Visiting either one shows you what an event meant and how you took part in it, without giving you power to alter it. The value of foreknowledge or hindsight lies in how it reshapes your response: mercy, acceptance and a changed life going forward.