Which is better for a traveler: to combine and shorten prayers with his companions on the road, or to pray with the congregation at a mosque when passing by one on the highway?

If you enter the mosque and find the prayer in progress, it is better to join the congregation and pray with them, to increase the reward through congregational unity. However, if you do not find the prayer in progress, it is better to pray in congregation among yourselves to attain the virtue of congregational prayer and the Sunnah of shortening (the prayer).