The Gemara teaches:
Rabbi Ḥiyya bar Abba said: One should always pray in a house with windows, as it is stated regarding Daniel: “And when Daniel knew that the writing was signed, he went to his house. In his attic there were open windows facing Jerusalem, and three times a day he knelt upon his knees and prayed and gave thanks before his God, just as he had done before” (Daniel 6:11).
Rashi explains that the need for windows is so one will be able to see the expanses and the sky, while Talmidei Rabbeinu Yonah suggest that the windows were necessary to further illuminate the synagogue, as light has a salutary effect and facilitates one’s focus on his prayer.
In the Tosefta, additional halakhot were derived from Daniel’s prayer.
I might have thought that one could pray as many times as he wishes throughout the entire day; it has already been articulated by Daniel, with regard to whom it is stated: “And three times a day he knelt upon his knees and prayed.” This teaches that there are fixed prayers.
I might have thought that this practice of fixed prayer began only when he came to the Babylonian exile; it was stated: “Just as he had done before.”
Further, I might have thought that one may pray facing any direction he wishes; the verse states: The appropriate direction for prayer is “facing Jerusalem.”
Daniel does not describe how these three prayers are distributed during the day.
I might have thought that one may include all three prayers at one time; it has already been articulated by David that one may not do so, as it is written: “Evening and morning and noon, I pray and cry aloud and He hears my voice” (Tehillim 55:18).
Furthermore, I might have thought that one may make his voice heard in his Amidah prayer; it has already been articulated by Hannah in her prayer, as it is stated: “And Hannah spoke in her heart, only her lips moved and her voice could not be heard” (I Shmuel 1:13).
Thus, the Rabbinic Sages established the normative rules and regulations of prayer based on the actions of biblical characters as they are presented in the written Torah.