Set up a recurring Apple Cash payment

>>Set up a recurring payment in Wallet

You can send weekly, biweekly, or monthly Apple Cash payments with Apple Cash.

1. On your iPhone, open the Wallet app. Then tap your Apple Cash card.

Tap the More button, tap Recurring Payments, then tap New Recurring

1. Add the recipient, then follow the on-screen instructions to choose the dollar amount of each payment, the date you want the payments to start, and how often you'd like them sent. You can also add a memo to identify what the payments are for.
2. Tap Send, then tap the Send button to review the payment.
3. Double-click the side button to pay. 
4. Confirm your payment with Face ID, Touch ID, or your passcode.<<

The Apple Support article I shared the link to below has additional information including how to pause and stop a recurring payment.

Send and receive money with Apple Cash - Apple Support