The 233rd prohibition is that we are forbidden from sending away empty-handed a Jewish servant who has worked for us when he goes free at the end of six years. We are obligated to give him gifts from our possessions.
The source of this prohibition is G‑d's statement1 (exalted be He), "When you send him away free, do not send him empty-handed."
The details of this mitzvah, which is called the mitzvah of ha'anakah, are explained in the beginning of tractate Kiddushin.