What is the ruling on a traveler who led residents in the Dhuhr prayer with four rak'ahs, then prayed Asr with two rak'ahs individually thereafter, despite him being the most knowledgeable among them?

If the traveler is an Imam for residents and leads them in Dhuhr prayer with four rak'ahs, or shortens it, their prayer is valid and sufficient. It is permissible for the traveler, as an Imam, to shorten the 'Asr prayer alone and combine it with Dhuhr. If a traveler prays behind a resident Imam, he must complete the prayer (i.e., pray the full four rak'ahs). If he wishes to combine and shorten 'Asr, he may do so after completing the first prayer.