Open the Messages app
Select the conversation or start a new message
Type your text message
Press and hold the Send button
Tap Send with effect
Choose Invisible Ink for a timed reveal effect
Tap the Send button to send the message
If you mean a scheduled text, use the Shortcuts app
Open Shortcuts
Tap Automation
Tap Create Personal Automation
Choose Time of Day
Set the time and repeat options
Tap Next
Add the Send Message action
Enter the recipient and message
Turn off Ask Before Running if available
Tap Done