Why was the fear prayer legislated?

The fear prayer (Salat al-Khawf) was legislated as a facilitation for Muslims and a protection for them from their enemy. The noble verses have mentioned its rulings, and if the fear intensifies, gesturing suffices. The prayer was made lighter to enable the worshipper to be present and attain humility (khushu'), and this is out of Allah's mercy and the ease of the Sharia. It was also legislated to maintain congregational prayer.