Sifrei Mitzvot do Powtórzonego Prawa 10:20

To pray daily is an affirmative duty, as it is said, "And ye shall serve the Lord, your God" (Exodus 23:25). The service, here referred to, according to the teaching of tradition, is Prayer, as it is said, "And to serve Him with all your heart" (Deuteronomy 11:13), on which the sages commented, "What may be described as Service of the Heart? Prayer". The number of prayers is not prescribed in the Torah. No form of prayer is prescribed in the Torah. Nor does the Torah prescribe a fixed time for Prayer.

Hence, women and slaves are under an obligation to pray, this being a duty, the fulfillment of which is independent of set periods. The obligation in this precept is that every person should daily, according to his ability, offer up supplication and prayer; first uttering praises of God, then, with humble supplication and petition ask for all that he needs, and finally offer praise and thanksgiving to the Eternal for the benefits already bestowed upon him in rich measure.

One who was fluent, would offer up many prayers and supplications. If one was slow of speech, he would pray as he could and whenever he pleased. Thus also, the number of separate services depended on an individual's ability. One would pray once daily; others, several times in the day. All, however, turned during prayer to the Sanctuary, in whichever direction that might be. This was the uniform practice from the times of Moses to those of Ezra.