What is the ruling on an individual performing prayer alone at home without an excuse?

Congregational prayer is obligatory for adult men, and it is not a condition to perform it in the mosque, even though performing it there is better and carries greater reward. So, whoever prays in his home congregationally commits no sin, but he misses out on the immense virtue of congregational prayer in the mosque. As for whoever prays individually, he incurs sin, unless the mosque is so far away that he cannot hear the call to prayer. Maintaining congregational prayer in the mosque is among the greatest signs of faith.