This article explains how to forward text messages on an iPhone running iOS 12 or later. The process is similar for iOS 7 and later, but the specific steps may vary in earlier versions of iOS.
How do I forward a text message? | iPhone tips
To forward a text message on iPhone using the Messages app that comes on iPhones and iPads, follow these steps:
Select the conversation containing the message you want to forward.
Tap and hold the message you want to forward until a pop-up menu appears. The menu offers options like Copy and More, plus reply options above the text message.