Hello,
I have tried to recover lost password of system user but unable to recover.
$ ./cypher-shell -d system
Connected to Neo4j 4.0.2 at neo4j://localhost:7687 .
Type :help for a list of available commands or :exit to exit the shell.
Note that Cypher queries must end with a semicolon.
@system> ALTER USER system SET PASSWORD 'neo4jsys';
Failed to alter the specified user 'system': User does not exist.
Please let me know that how rcover system user password.
Yes, it's a bit of semantics, but it's also being precise 
You can reset a password but you cannot recover the old one. Hope this is helpful.
edit: I just noticed the section heading in the docs "Recover a lost password" - good catch @boydkelly I've notified the doc team
oh brother, isn't this just semantics? Well lets see: The link you sent explains how to a lost password. So neo4j thinks this is ok. But in any case, whether you want to recover reset or whatever a password , those instructions in the link you sent tell you how to do it. The instruction above doesn't.
You cannot recover a password - that would be a "bad thing" when it comes to security. The Password and User Recovery section of the docs tell you how to deal with the situation.
This does not seem to help to 'recover' a password as the command output specifically states:
IMPORTANT: this change will only take effect if performed before the database is started for the first time.
The command itself also clearly implies set-**initial-**password. So how then do you 'recover' the password as asked in the question?