The ruling on one who prays on the Day of Tarwiyah without joining a congregation

The question: He has several questions, but the answer came while responding to his first question. However, his fifth question is the one that causes confusion for the questioner, Abdullah Ali Sulayman al-Asmari, who says: A pilgrim prayed the midday prayer alone at 'Arafah on the Day of Tarwiyah, and he also prayed the afternoon prayer alone, and he prayed the sunset prayer alone, and he prayed the night prayer alone. What is his ruling? Please inform us, may Allah reward you with good for us?
The answer: He sees that he prayed alone, meaning, he was with no one and did not pray in a congregation. This is the apparent case, and there is no blame on him, meaning: his prayer is valid. But he erred and sinned by not performing the prayer with the congregation. The prayer is valid, if Allah wills, but he must repent to Allah; because he left the congregation, and the congregation is obligatory. The congregational prayer is an obligatory command, and the prayer is valid, and there is nothing wrong with the Hajj. Rather, he must repent to Allah , because it is obligatory for the pilgrim to pray with the congregation. The congregation that is with him in his lodging, or the other congregations, or in the Musjid al-Khaif if he is in Mina. The point is that he should seek out the congregation, look for the congregation, and pray with the congregation, and not pray alone.