http://wccftech.com/face-id-supporting-apple-pay/

Face ID could be a very suitable alternative you need in the iPhone 8 to seamlessly get through the home screen without even using your fingers to do the job. Now there is going to be one more thing added to its flexible repertoire and that is being to authenticate payments. According to leaked iOS 11 firmware, it appears that authorizing payments using Apple Pay is going to be a walk in the park since the use of Face ID is expected to simplify the process.

According to this leaked iOS 11 firmware, the process to initiate payments will start from using Face ID to authorize if the owner of the iPhone 8 is indeed transferring funds or not. With Apple Pay expected to be a secure platform to authenticate payments, the inclusion of Face ID will make the process ever so simple.