שלום וברכה!
[ט"ו אד"ר, תשי"ט]
בזח"ג רצג, ב (ועוד בכ"מ בזח"ג) איתא אשר ענין ויקץ כישן הוי' הוא בשם הוי' ולא אד' וכ"מ בתניא פי"ט (מדבארו על חכ' שבנפש)
ומפי' הענינים בזח"ג שם וס' הליקוטים להאריז"ל לתהלים סי' מד מוכח דגם ענין למה תישן הוי' הוא בשם הוי' (מדפרשו על דורמיטא דז"א).
Shalom u'Vrachah! [15 Adar II, 5719] In Zohar III, 292b (and also elsewhere in Zohar III), it is stated that the matter of 'Vayikatz K'yashen Havayah' ('He awoke as one asleep, Havayah') refers to the name Havayah and not Ad-nai. Similarly, this is found in Tanya chapter 19 (in its discussion about wisdom of the soul). From the explanations of these matters in Zohar III there and Sefer HaLikutim by the Arizal on Tehillim chapter 44, it is evident that also the matter of 'Lamah Tishan Havayah' ('Why do You sleep, Havayah') refers to the name Havayah (as they explain it regarding the dormita of Zeir Anpin).
Summary
This letter clarifies that both verses—'Awaken, L‑rd' and 'Why do You sleep, L‑rd'—refer specifically to the Divine name Havayah, not Ad-nai, as explained in Zohar and Tanya.