Berakhot 6B

וכולהו כתיבי באדרעיה.

in the tefillin of the head, where there are 4 separate compartments. And all of the verses are written together on one parchment in the tefillin of the arm, which has only one compartment.

אמר רבין בר רב אדא, אמר רבי יצחק: כל הרגיל לבא לבית הכנסת ולא בא יום אחד, הקדוש ברוך הוא משאיל בו, שנאמר: ״מי בכם ירא ה׳ שמע בקול עבדו אשר הלך חשכים ואין נגה לו״.

Additionally, Ravin bar Rav Adda said that R' Yitzḥak said: One who is accustomed to come to the synagogue and did not come one day, God asks about him, as it were, to determine what happened to him, as it is stated: “Who among you fears YHWH? Who hears the voice of His servant? Though he walks in darkness and has no light, let him trust in the name of YHWH, and rely upon his God” (Isaiah 50:10). In other words, God asks, who among you fears YHWH yet did not come to hear the voice of His servant the prayer leader, who engages in the service of God? He who went out before dawn and walks in darkness before prayer.

אם לדבר מצוה הלך ⁠— נוגה לו, ואם לדבר הרשות הלך ⁠— אין נוגה לו.

If it is for a matter involving a mitzva that he went and absented himself from prayer in the synagogue, then, despite the darkness, there is light for him, the aura of his mitzva will protect him. But if it is for an optional matter, some mundane purpose, that he went and absented himself from prayer in the synagogue, then, even once the day begins, there is no light for him (Maharsha).

״יבטח בשם ה׳״ מאי טעמא? משום דהוה ליה לבטוח בשם ה׳, ולא בטח.

The verse continues: “Let him trust in the name of YHWH.” The Talmud asks: What is the reason that God is so exacting with this person? The Talmud answers: Because he should have relied on the name of YHWH, and trusted that he would not incur any loss if he postponed dealing with his mundane matters until after prayer in the synagogue, and he did not rely on God.