Guide for the Perplexed, by Moses Maimonides, Friedländer tr. [1904], at sacred-texts.com
ALTHOUGH the two roots naẓab and yaẓab are distinct, yet their meaning is, as you know, identical in all their various forms.
The verb has several meanings: in some instances it signifies "to stand or "to place oneself," as "And his sister stood (va-tetaẓẓab) afar off" (Exod. ii. 4); "The kings of the earth set themselves" (yiyaẓẓebu) (Ps. ii. 2); "They came out and stood" (niẓẓabim) (Num. xvi. 27). In other instances it denotes continuance and permanence, as, "Thy word is established (niẓẓab) in Heaven" (Ps. cxix. 89), i.e., it remains for ever.
Whenever this term is applied to God it must be understood in the latter sense, as, "And, behold, the Lord stood (niẓẓab) upon it" (Gen. xxviii. 13), i.e., appeared as eternal and everlasting "upon it," namely, upon the ladder,
the upper end of which reached to heaven, while the lower end touched the earth. This ladder all may climb up who wish to do so, and they must ultimately attain to a knowledge of Him who is above the summit of the ladder, because He remains upon it permanently. It must be well understood that the term "upon it" is employed by me in harmony with this metaphor. "Angels of God" who were going up represent the prophets. That the term "angel" was applied to prophets may clearly be seen in the following passages: "He sent an angel" (Num. xx. 16); "And an angel of the Lord came up from Gilgal to Bochim" (Judges ii. 1). How suggestive, too, is the expression "ascending and descending on it"! The ascent is mentioned before the descent, inasmuch as the "ascending" and arriving at a certain height of the ladder precedes the "descending," i.e., the application of the knowledge acquired in the ascent for the training and instruction of mankind. This application is termed "descent," in accordance with our explanation of the term yarad (chapter x.).
To return to our subject. The phrase "stood upon it" indicates the permanence and constancy of God, and does not imply the idea of physical position. This is also the sense of the phrase "Thou shalt stand upon the rock" (Exod. xxxiii. 21). It is therefore clear that niẓẓab and ‘amad are identical in this figurative signification. Comp. "Behold, I will stand (‘omed) before thee there upon the rock in Horeb" (Exod. xvii. 6).