Exodus 17:1

And all the congregation of the sons of Israel journeyed from the desert of Sin by their journeyings according to the word of the Lord, and they encamped in Rephidim, a place where their hands were idle in the commandments of the law, and the fountains were dry, and there was no water for the people to drink.

AND ALL THE CONGREGATION OF THE CHILDREN OF ISRAEL JOURNEYED FROM THE WILDERNESS OF SIN, BY THEIR STAGES, ACCORDING TO THE COMMANDMENT OF THE ETERNAL, AND THEY ENCAMPED IN REPHIDIM. Scripture is stating that they journeyed from the wilderness of Sin, where they were encamped after they had set out from Elim, and covered various stages of their journey in accord with G-d’s command. Afterwards, they encamped in Rephidim. Scripture thus relates briefly here that when they first journeyed from the wilderness of Sin, they pitched in Dophkah, and afterwards in Alush, and from Alush they came to Rephidim. This is the meaning of the expression here, by their stages, since there were many stages by which they came from the wilderness of Sin to Rephidim, and they did not reach it on the first journey. Scripture, however, [omits all these various stages here] because its only concern is to explain their murmuring. At the beginning of their arrival in that wilderness [of Sin], they complained for bread, and now they quarreled [with Moses] over water, [as it is said], and there was no water for the people to drink. When they came to that place and did not find fountains of water, they at once quarreled with Moses. This is the meaning of the expression, Wherefore the people did quarrel with Moses, for the murmurings mentioned in places where Scripture says, and they murmured, mean complaints, i.e., that they were declaring their grievances about their condition, saying, “What shall we do? What shall we eat, and what shall we drink?” But vayarev (and he quarreled) means that they did actually make quarrel with Moses, coming to him and saying, “Give us water, you and Aaron your brother, for you are responsible, our blood is upon you.” And Moses said to them, “Why quarrel ye with me? Wherefore do ye try the Eternal? This quarrel is to test G-d, that is whether He can give you water. If you will hold your peace and let me alone and instead pray to Him, perhaps He will answer you.” And indeed, it was their intent to try [G-d], as Scripture says, And the name of the place was called Massah (Trying) and Meribah (Quarrel), because of the quarrel of the children of Israel and because they tried the Eternal, saying: Is the Eternal among us, or not? Then their anger against him relented, and for a day or two, they were supplied by the waters in their vessels. But afterwards, the people thirsted there for water, and the people murmured against Moses, something like the complaints they made whenever they wanted something, saying, Wherefore hast thou brought us up out of Egypt? When Moses saw that they thirsted for water, he prayed to G-d and recounted before Him his distress when they first quarreled with him.
Rabbi Abraham ibn Ezra said that there were two groups: one that quarreled [with Moses because they had no water to drink], and one [that had water which they brought from Alush, the place where they were encamped before coming to Rephidim, but] who tested G-d [to see if He would give them water]. The correct interpretation is as I have explained.

לשתות העם, that the people could drink. The unusual construction is similar to Genesis 16,3 לשבת אברהם.