This is a security warning notification message from Facebook. When the account trying to send you messages has been hacked or interfered with and some messages have been sent through it, Facebook alerts the person receiving the message with this kind of notification. Upon Facebook receiving a report of an account hacking they will lock the account and then send this notice to anyone who tries to send message to that account. It will also appear when there is need for an account verification for whatever reason.
“This Message has been temporarily removed because the sender’s account requires verification” can also appear when an owner of a Facebook account reports account as having been maliciously used.
When Facebook also locks an account for any reason this message the message they try to send and which previously send will show this kind of message. This can be corrected when the account is unlocked or the owner verifies the account.
Facebook may block or delete messages on your Facebook friend’s account and state identity needed to be verified. Bear in mind that they give no warning. So you may lose previous messages send via that account. Facebook does this to protect the receiver of the message from.