The instructions were to be sure to get the check before he left the company, because one time they had left one. This situation represents a risk to the check recipient, since the passage of time may result in there being no cash left in the issuer's bank account to be used to pay the amount listed on the check when it is eventually presented to the bank for payment. On that note, don't sign checks before writing the payee and amount.
The content provided is for informational purposes only, without representation or warranty of any kind. If you mess up, write a new check instead of crossing out information on the old one. How are banks letting their customers know that they shouldn't post-date cheques?