Sure, getting a preview of your incoming text messages without needing to unlock your device is handy—but there are some times when you might not want everyone in eyeshot of your iPhone, iPad, or iPod touch to see what you’re discussing with the person on the other end. Luckily, iOS offers a super-easy way to stop this.
Open the Settings app, tap on Notifications, and tap on Messages. Scroll down the screen a bit, and you’ll see an toggle for Show Preview.
Set this to off, and you won’t see anything more than an alert telling you who your new message is from. [via CoM].