Isaac went out to pray in the field toward evening.
Bereishit 24:63
We recite the morning prayer before beginning our workday and the evening prayer after completing the day's activities. In contrast, the afternoon prayer requires us to stop in the midst of our mundane affairs and focus on G-d.
Our daily, mundane affairs are symbolized by "the field," the area outside the city limits, which is untamed and uncultivated. Through prayer in the afternoon, Isaac transformed "the field" into a place of prayer to G-d.
The morning prayer undeniably serves as our principal daily renewal of Divine consciousness. Nonetheless, afterward, it remains to be seen how we will fare when we go out into "the field." Will the secular and material influences of "the field" cause us to lose the spiritual awareness and closeness to G-d that we achieved during the morning prayer? By pausing in the middle of our mundane affairs in order to recite the afternoon prayer, we demonstrate that our involvement in material affairs does not separate us from G-d.
--From Kehot's
Daily Wisdom #2