Who says "Solu Solu", and why?
Rashi: The Navi says so in My name, to My nation. Pave a path.
Radak: One who trusts in Me will say so when the enemy is plagued. This command is not to anyone particular, rather, to anyone, like "Re'eh Rei'ach Bni" (Bereishis 27:27) and similar verses. Refer to 57:14:3:2-3.
Why does it add "Panu Derech"?
Rashi: Clear the Yetzer ha'Ra from your ways.
Malbim: Solu commands to make a new path where there is no path. Where there is a path, but it was ruined, clear it! Where there is a good path, just it has stumbling blocks, "Harimi Michshol"! These three correspond to teaching those who never knew Derech Hashem, those who knew and forgot, and those who know, just their Yetzer ha'Ra is a Michshol for them.
What is the meaning of "Harimi Michshol"?
Rashi: Remove the stones on which your feet stumble, i.e. your thoughts of evil.
Radak: The big stumbling block that was on the road was lifted, i.e. the enemy; who did not allow Yisrael to come to Yerushalayim. Now remove stumbling blocks on the road, and Yisrael can go calmly and securely. Put stones on roads that are ruined via mud, to raise them; it is normal to do so 1 .
Radak citing Targum Yonasan: Remove stones from the road, lest people and animals stumble on them.
Radak (13): This world is called Michshol; lifting it is Teshuvah.
I.e. lest people slip on the mud. It is clear from his Perush below (62:11) that this is his intent.
