Rock [ṣur] is an equivocal term. It is a term denoting a mountain. Thus: And thou shalt smite the rock.1 It is also a term denoting a hard stone like flint. Thus: Knives of rock.2 It is, further, a term denoting the quarry from which quarry-stones are hewn. Thus: Look unto the rock whence ye were hewn.3 Subsequently, in derivation from the last meaning, the term was used figuratively to designate the root and principle of every thing. It is on this account that after saying: Look unto the rock whence ye were hewn, Scripture continues:4 Look unto Abraham your father, and so on,5 giving, as it were, an interpretation according to which the rock whence ye were hewn is Abraham your father. Tread therefore in his foot-steps, adhere to his religion, and acquire his character, inasmuch as the nature of a quarry ought to be present in what is hewn from it. On account of the last meaning, God, may He be exalted, is designated as the Rock, as He is the principle I and the efficient cause of all things other than Himself. Accordingly it is said: The Rock, His work is perfect;6 Of the Rock that begot thee thou wast unmindful;7 Their Rock had given them over;8 And there is no Rock like our God;9 The Rock of Eternity.10 The verse And thou shalt stand erect upon the rock11 means: Rely upon, and be firm in considering, God, may He be exalted, as the first principle. This is the entryway through which you shall come to Him, as we have made clear when speaking of His saying [to Moses]: Behold, there is a place by Me.12