When Rivka was coming to meet Yitzchak the Torah says: VAYETZE YITZCHAK LASU’ACH BASADEH LIFNOT AREV, “Yitzchak went out to the field to meditate…”. (Gen. 24,63) According to Chazal, Yitzchak was reciting the Mincha service.
Mincha is different from Shacharit and Aravit in a very significant way. Shacharit is recited in the morning when one gets up from his sleep and has not yet encountered the world and the problems of the day. He therefore can concentrate on his prayers and express his true feelings.Aravit is also a time when the activities of the day are over and the problems of the day are laid to rest. The worshipper is approaching his rest and is beginning to appreciate the coming peace.
Mincha, however, is recited in the middle of the day’s action. One has to stop whatever he is doing and start concentrating on his prayers and communicate with Hashem. This is not very easy. That is why Chazal said: LE’OLAM YIZAHER ADAM BETFILLAT HAMINCHA, “A person should always take special care about the Mincha prayer.” (Ber. 6b)
Yitzchak started the practice of Mincha in the field. The field in ancient times represented business or the means of livelihood. (e.g. Esav was a man of the fields.) Today, also, one should be especially careful with this service and not let his business or other activities interfere with his obligations to Hashem.