Verse 1 already said that Hashem brought him there!
Malbim: Initially, He brought him close to the mountain ? "va'Ynicheni El Har" (2). "El" shows that he was not yet there. Hashem wanted him to see it from afar. Now He brought him to the Kadosh place at the top of the mountain.
What is "k'Mar'e Nechoshes"?
Rashi: It is like the radiance of the Chayos, like it says above "v'Notzetzim k'Ein Nechoshes Kalal" (1:7).
Radak: It is as if he saw an angel in the form of a man measuring the building. This is like it says about Yehoshua, "v'Hinei Ish Omed l'Negdo" (Yehoshua 5:13). Malbim ? he saw that the future Binyan will not be via people, rather, via upper beings, in a wondrous way.
Why did he have a linen thread?
Rashi: Nothing is better for measuring land than a linen rope.
Why did he have a measuring rod?
Rashi: It was to measure the thickness of the wall, and the length and width of the gates. Radak, Malbim ? a rope is used for a big measure on the ground. A rod is used for a small measure, e.g. of a building.
What gate was he standing in?
Radak (here and 21): It was the [Malbim ? eastern] gate of Har ha'Bayis.
