If you want to recover a text message, tap on the thread or message so that it's selected, hit Recover on the bottom right, ...

Text messages have a reputation for being informal and inconsequential, but you might have really critical information in there. So, if you’ve deleted some texts to clear up space on your iPhone ...

What You’ll Need: A recent backup of your device created before the message was deleted. This method relies on the assumption that your phone was backed up before the text was deleted.