What do we learn from "Melech b'Yafyo Sechezenah Einecha"?
Yuma 78b: Due to this, some say that the king may wash his face on Yom Kipur.
Ta'anis 17a: Due to this, the king cuts his hair every day.
Rashi #1: You will merit to see from a far land your king in his glory.
Rashi #2: You will see Hashem from afar - you will see miracles and grandeur that I will do for you. Also refer to 33:19:3:1.
Rashi #3: I tell you, the Tzadik, that you will merit to see the radiance of the Shechinah.
Radak: The king is Chizkiyah. "Your eyes" refers to Shevet Yehudah. Until now, your eyes saw Melech Ashur (refer to 33:17:2:2). You will no longer see him, rather, this king you will see in his beauty. He will not fear; he will sit on his throne in honor - "va'Yinasei l'Einei Kol ha'Goyim" (Divrei ha'Yamim II, 32:23). "Melech" refers to both, as if it says Melech b'Yafyo Sechezenah Einecha Tir'enah Melech Eretz Marchakim.
Malbim: It said that due to Chizkiyah's virtue, you need not fear Melech Ashur. In truth, at the time you see Chizkiyah in his beauty, you will see also a king from afar (Melech Ashur) in his 'beauty' (many troops).
What is the meaning of "Tir'enah Eretz Marchakim"?
Rashi citing Targum Yonasan: You will see those who descend to the land of Gehinom.
Radak: Until now, your eyes saw a king from afar - Melech Ashur. Initially they served him, and saw his face with the gift that they would bring to him.
Malbim: Refer to 33:17:1:7.