Commentary for Kiddushin 61:3
אמר רבי יהושע בן לוי אסור לאדם שיהלך ארבע אמות בקומה זקופה שנא' (ישעיהו ו, ג) מלא כל הארץ כבודו רב הונא בריה דרב יהושע לא מסגי ארבע אמות בגילוי הראש אמר שכינה למעלה מראשי
R'Isaac said: He who transgresses in secret is as though he pressed the feet of the Shechinah for it is written: Thus saith the Lord, The heaven is my throne, and the earth is my footstool.<span class="x" onmousemove="('comment',' Isa. LXVI, 1. By transgressing secretly he avers that God's presence is not there, and thus would confine the feet of the Shechinah into a narrower place than what they occupy, viz., the whole earth.');"><sup>2</sup></span> R'Joshua B'Levi said: One may not walk four cubits with haughty mien,<span class="x" onmousemove="('comment',' Lit., 'upright stature.');"><sup>3</sup></span>
Rashi on Kiddushin
Daf Shevui to Kiddushin
The second two statements deal with the proper posture and clothing to acknowledge that God is only slightly above one’s head. This last statement is one of the sources used to prove that Jews must keep their heads covered.