Krdytkyu

In D&D (Forgotten Realms) lore, is there any kind of answer for how long it takes the soul to leave the body after death? If not, is there any answer implied by other rules or effects (such as resurrection spells)?

The reason I ask is because I think that this might be the reason that revivify does not require the soul to be willing whereas other spells do (since revivify must be done within a minute after death (Basic Rules, p. 104)).

Though I am asking about 5e, answers supported by earlier edition lore can be considered.

The rules don't specify; revivify's limit is a good starting point

As with a lot of things, the D&D 5e rules leave a lot of latitude for interpretation. @Aviose came up with a good conceptual model in a comment on an answer to a question about souls in 2015.
_{I'm taking this opportunity to pull it out of a comment and put it into an answer that it fits.}

Best way to view revivify working is simply stating that it takes
about one minute (maybe more) for the soul to leave the body upon
death. Consider that the in-world time to brain-death and look at revivify as an advanced form of CPR.

Of interest: I was looking in my 1e and 2e AD&D material and find that the explicit link between souls and raise dead / resurrect spells comes from 3e and later. I'll follow up with BECMI/BX info when I get back to where that is

An example of the immediate departure of a soul in FR is Kelemvor's soul:

Kelemvor's soul was absorbed into Cyric's sentient sword, Godsbane, in the moment he was killed on top of Blackstaff Tower.

Given the agency and nature of the sword involved, that may be an exception rather than a rule (This appears to be during the FR's AD&D 2e continuity, Prince of Lies).

On DMG page 24, under "Bringing Back the Dead", it states that you cannot bring back the soul of an unwilling creature:

A soul can’t be returned to life if it doesn’t wish to be. A soul knows the name, alignment, and patron deity (if any) of the character attempting to revive it and might refuse to return on that basis. For example, if the honorable knight Sturm Brightblade is slain and a high priestess of Takhisis (god of evil dragons) grabs his body, Sturm might not wish to be raised from the dead by her. Any attempts she makes to revive him automatically fail. If the evil cleric wants to revive Sturm to interrogate him, she needs to find some way to trick his soul, such as duping a good cleric into raising him and then capturing him once he is alive again.

I quote the fact that the chapter says bringing back from the dead, and revivify states “You touch a creature that has died”.

Another thing to consider 5e is when a PC gets below 0 they go into death saving throws, which is the character fighting off death before dying.

From all that I assume the soul leaves the body the moment you die.

In my opinion, this rule also protects players from not being able to die when their character is super tired of things or done with life but circumstance keeps trying to bring them back. It has also protected me as a GM from player shenanigans.