GEN385 Do not enter another person’s house suddenly, thereby catching the person unawares.  In modern terms, this means calling ahead.  When Adam ate of the fruit from the forbidden tree, God hid Himself, as it were, to the entrance to the Garden of Eden, and called out to Adam, “Where are you?” God, the all-knowing, obviously knew exactly were Adam was, but He did not wish to startle him Derech Eretz Rabbah 5:2, Niddah 16b, Pesachim 112a.  So, God called out, and gave Adam time to adjust to His presence.  We, too, should take care not to startle others.  The directive applies in one’s own home as well: “Rabbi Shimon bar Yochai said: The man who enters [even] his own house … unexpectedly, the Holy One hates” Leviticus Rabbah 21:8. Thus, parent should always knock before entering their children’s rooms; everyone, children as well as adults, is entitled to privacy. TELVOL 1:131-2