Het geeft dit aan:

walletpassphrase "passphrase" timeout

Stores the wallet decryption key in memory for 'timeout' seconds.
This is needed prior to performing transactions related to private keys such as sending bitcoins

Arguments:
1. "passphrase" (string, required) The wallet passphrase
2. timeout (numeric, required) The time to keep the decryption key in seconds.

Note:
Issuing the walletpassphrase command while the wallet is already unlocked will set a new unlock
time that overrides the old one.

Examples:

unlock the wallet for 60 seconds
> bitcoin-cli walletpassphrase "my pass phrase" 60

Lock the wallet again (before 60 seconds)
> bitcoin-cli walletlock

As json rpc call
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "walletpassphrase", "params": ["my pass phrase", 60] }' -H 'content-type: text/plain;' http://127.0.0.1:8332/
(code -1)

I have no idea what to do now.