What is required of one who prayed Dhuhr and Asr, combined in advance, in Arafat, and attended the prayer but did not attend the sermon?

The sermon on the Day of Arafah takes place before the Dhuhr and Asr prayers, which are combined and offered early (jam' taqdim). It is a Sunnah (definition) (recommended act), not an obligation. Therefore, there is no harm if it is omitted. Similarly, if some pilgrims do not listen to it, there is no harm in that, nor is anything due from them. However, they miss out on the virtue by omitting it or by not listening to it.