Facebook recommends minimal or no text in images to help the deliverability of the ad. Text cannot take up more than 20% of the visual space in your ad, or Facebook will begin to throttle delivery. The ad will cost more to reach your target audience or be rejected by Facebook altogether.
Think carefully about what you want to say and work the text you would have in the ad image into the Headline and Text fields that surface above and below your image.
You can also test your image using Facebook’s text overlay tool to ensure the image will work for your ad.