That is that we are commanded to serve Him. And this command is repeated several times: His saying, "And you shall serve the Lord, your God" (Exodus 23:25); and His saying, "and you shall serve Him" (Deuteronomy 13:5). And although this command is from the inclusive commands - as we explained in Principle Four (Sefer HaMitzvot, Shorashim 4) - it nevertheless has specificity, since it is the command to pray. The language of the Sifrei is, "'And to serve Him' (Deuteronomy 11:13) - that is prayer." And they also said, "'And to serve Him' - that is [Torah] study." And in the Mishnah of Rabbi Eliezer, the son of Rabbi Yose HaGelili, they said, "From where [do we know that] the essence of prayer is a commandment? From here - 'You shall fear the Lord, your God, and you shall serve Him' (Deuteronomy 6:13)." And they said, "Serve Him through His Torah; serve Him in His Temple." This means, direct [yourself] towards it, to pray [towards] there, as Shlomo, peace be upon him, explained.

(15) Inner mindfulness: how does one attain it? Any prayer for which one is not fully mindful is not considered prayer. And if one prays without mindfulness, one must go back and pray [again, this time] with mindfulness. One who is confused or inwardly agitated is forbidden from praying until he settles himself; thus, one who has come in from traveling and is tired or unsettled is forbidden from praying until he settles himself. The sages used to say that he ought to wait for three days until he has rested and his emotions have cooled, and only afterward may he pray.

(16) How is intent (achieved)? A person should turn his heart from all thoughts and envision himself as if he is standing before the presence of God. Therefore he must sit a while before prayer in order to direct his heart and then he can pray with ease and supplications. And he should not treat his prayer like one who is carrying a burden and throws it down and moves on. Therefore he must sit a while after prayer and then take leave. The early pious individuals would wait an hour before prayer and an hour after prayer and would draw out their prayer for an hour.

(15) There are three things which a person must look into and consider well in order to acquire such fear. The first is that he is actually standing in the presence of the Creator, Blessed be His Name, and communicating with Him, even though He cannot be seen. This is the hardest of the three for a person to create a true picture of in his heart, for he is entirely unaided by his senses towards this objective. However, one who is possessed of sound intelligence will, with a little thought and attention, be able to implant in his heart the truth of his actually communicating with the Blessed One, of His imploring and entreating Him and being heard and listened to by the Blessed One in the same way that a man, speaking to his friend, is heard and listened to by him.

(13) And the Lord said: Forasmuch as this people draw near, and with their mouth and with their lips do honour Me, But have removed their heart far from Me, And their fear of Me is a commandment of men learned by rote;

(5) No shrub of the field was yet in the earth, and no herb of the field had yet sprung up; for the LORD God had not caused it to rain upon the earth, and there was not a man to till the ground;

Because there was no man to work the soil, and no one recognized the benefit of rain, but when man came and understood that they were essential to the world, he prayed for them, and they fell, and the trees and the herbs sprouted. — [from Chul. 60b]