Missed asr prayer and maghrib started in masjid
Sheikh al-Islam Ibn Taimiyya (may the mercy of Allah be upon him) said that he should pray maghrib with the imam (prayer leader), then pray asr afterwards, as agreed upon by all leading scholars. The question of does he repeat maghrib has two scholarly opinions: the first is that he repeats. This is the saying of Ibn Omar, Malik, Abi Hanifa and Ahmad in what is most well-known about this issue. The second opinion is that he does not repeat. This is the saying of Ibn Abbas, the Shafiei madhab, and the second opinion of Ahmads school of thought.
The latter is more correct, for Allah did not make it obligatory on the person to pray a salaat twice if he has feared Allah as much as he can (wallahu a'lam [and Allah knows best]).1
From the book What Should You Do in the Following Situations... ?
1 Majmooa Fatawi Ibn Taimiyya 22/106.