אורח חיים צ״הOrach Chayim 95

Se’if 1א׳

יְכַוֵּן רַגְלָיו זֶה אֵצֶל זֶה בְּכִוּוּן, כְּאִלּוּ אֵינָם אֶלָּא א', לְהִדָּמוֹת לְמַלְאָכִים דִּכְתִּיב בָּהֶן: וְרַגְלֵיהֶם רֶגֶל יְשָׁרָה (יְחֶזְקֵאל א, ז) כְּלוֹמַר: רַגְלֵיהֶם נִרְאִים כְּרֶגֶל אֶחָד וְיֵשׁ אוֹמְרִים כְּשֶׁעוֹמֵד לְהִתְפַּלֵּל יֵלֵךְ לְפָנָיו ג' פְּסִיעוֹת, דֶּרֶךְ קֵרוּב וְהַגָּשָׁה לַדָּבָר שֶׁצָּרִיךְ לַעֲשׂוֹת (רוֹקֵחַ).

The Position of One's Limbs at the Time of Prayer, containing 4 s'ifim One should position one's feet next to each other as though they are one, in order to imitate angels, as it written regarding them: “their feet were a straight foot” [(Ezekiel 1:7)], which is to say their feet appeared as one foot. (Some say when one stands to pray one should take three steps forward in the way of coming close and approaching a matter that must be done.) (Rokeach)

Se’if 2ב׳

צָרִיךְ שֶׁיָּכוֹף רֹאשׁוֹ מְעַט, שֶׁיִּהְיוּ עֵינָיו לְמַטָּה לָאָרֶץ, וְיַחֲשֹׁב כְּאִלּוּ עוֹמֵד בְּבֵית הַמִּקְדָּשׁ, וּבְלִבּוֹ יְכַוֵּן לְמַעְלָה לַשָּׁמַיִם.

One should bend one's head a little so that one's eyes will be downwards to the ground and one should consider oneself as if one is standing in the Beit Hamikdash, and in one's heart, one should direct [oneself] upward towards the heavens.

Se’if 3ג׳

מַנִּיחַ יָדוֹ עַל לִבּוֹ כְּפוּתִין, (פֵּרוּשׁ כִּקְשׁוּרִין) הַיְמָנִית עַל הַשְּׂמָאלִית, וְעוֹמֵד כְּעֶבֶד לִפְנֵי רַבּוֹ, בְּאֵימָה, בְּיִרְאָה וּבְפַחַד, וְלֹא יַנִּיחַ יָדָיו עַל חֲלָצָיו, מִפְּנֵי שֶׁהוּא דֶּרֶךְ יֻהֲרָא וע"ל רֵישׁ סי' צ"ז.

One should place one's hands over one's heart, as if bound (i.e. as if connected), the right [hand] over the left, and stand like a servant before one's teacher with terror, awe, and fear. And one should not place one's hands on one's hips, because that is the way of haughtiness (and see below in the beginning of Orach Chayim 97).