If you enter the text directly in the textbox and then display it, arabic is displayed, but when it is fetched from DB it may not be displayed based on the encoding in the DB.
Please see if your DB supports arabic and is UTF-8 encoded.
If the issue still persists, you might have to write a custom control. But as per now, it looks like the issue from the DB side.
To test that, create a text input > configure on change to "post value" and refresh section. Create another text input below in the same section to use the same property, but as read only just for displaying the value.
When u enter any arabic text in the first text input, see that whether the same is displayed in the second text box.