In Parshat Chayei Sarah, Breisheet 24:63 we read: “Yitzchak went to speak (lasuach) in the field towards evening. He raised his eyes and suddenly saw camels approaching.”

The Talmud, Brachot 26b teaches that from here we learn that Yitzchak established the Mincha (afternoon) payer:

The Talmud brings the opinion of Rabbi Yossi the son of Rabbi Chanina:

Avraham instituted the Shacharit prayer as it is stated (Breisheet 19:27) “And Avraham arose early in the morning to the place where he had stood (amad).” Standing (amida) refers to prayer as it says (Tehilim 106:30) “And Pinchas stood up and prayed.” Yitzchak instituted the Mincha prayer as it is stated (Breisheet 24:63) “Yitzchak went to speak (lasuach) in the field towards evening.” Speech (sicha) in this verse refers to prayer as it is stated (Tehilim 102:1) “A prayer for the afflicted man when he swoons, and before God he pours forth his speech.” Yaakov instituted the Maariv prayer as it is stated (Breisheet 21:11) “And he encountered (vayifga) the place and spent the night there.” The term pegiah refers to prayer as it is stated (Yirmiyahu 7:16) “And you, do not pray for this people, and do not take up from them a cray and a prayer, and do not entreat (tifga) me.”

In his book, Holistic Prayer, Rabbi Avi Weiss explains what made each of the Patriarch’s prayers spontaneous:

Avraham was an innovator, a trailblazer, a “morning person.” Avraham introduces the world to God and monotheism and therefore he prays at dawn, when the sun rises.

Rabbi Weiss characterizes Yitzchak as a meditator who evaluated and transformed Avraham’s ideas. He was a passive figure who followed in his father’s footsteps. He was taken to the Akeda (almost sacrificed), had a wife chosen for him and dug his father’s wells. He prays in the late afternoon, as the sun sets, a time suitable for contemplative thought.

Yaakov is considered by Rabbi Weiss to be the most tragic. He went through many trials and tribulations including having to run away from his brother. Maariv suits Yaakov as he prayed at night, when one is often overcome by fear and loneliness.

We see from here that all three of our main prayer services were founded spontaneously by the Patriarchs. We too each have a distinct personality. It is natural that particular people will feel closer to God at different times of day. Some connect to one Patriarch’s life story more than another’s. Others feel differently each day as well as at various points in their lives. The Patriarchs teach us that all of these paths are valid and although we now have set prayer, we should not lose the spontaneity through which the prayers were originally established.