What is the ruling on Tayammum for someone who finds water but does not have enough time to use it before the prayer time expires, and what is the ruling on the prayer of one who performs Tayammum if the prayer time expires while he is performing it?

The majority of scholars hold that the expiration of the prayer time invalidates tayammum. Some of them believe it invalidates it absolutely, while others believe it does not invalidate it if the person performing tayammum is already in prayer.

The Hanafis and some verified scholars are of the opinion that the expiration of the prayer time does not invalidate tayammum, so the person who performed tayammum may continue their prayer.

The first opinion is more cautious.