Is it permissible to combine and advance the Asr prayer with the Dhuhr prayer due to traveling a distance of 100 kilometers, knowing that the Dhuhr prayer was performed in congregation and half an hour before the Adhan of Asr?

It is not permissible to offer the prayer before its appointed time except in the authorized instances of combining prayers (Jam‘). For combining prayers with the intention of advancing the second prayer (Jam‘ al-Taqdim), the intention must be present when commencing the first prayer or before concluding it with the salutation. Furthermore, there should be no significant separation between the two prayers except for a brief interval, and the excuse permitting the combination must exist at the beginning of both prayers. The prayer mentioned is invalid because it was offered before its time and because the conditions for the validity of combining prayers were not met. It should also be noted that the concession for travel (rukhsat al-safar) is not availed until one has departed from the place of travel.