וַיָּבֹ֖א עֲמָלֵ֑ק וַיִּלָּ֥חֶם עִם־יִשְׂרָאֵ֖ל בִּרְפִידִֽם׃
E veio Amalek e guerreou contra Israel em Refidim.
Siftei Chakhamim
He heard that Aharon died and [the clouds of glory] departed. You might ask: What is Rashi’s source for this? Perhaps [the explanation of the verse] is like its plain understanding, that it was because “Yisroel had come…” as the verse continues. The answer is that Rashi is answering the question: Why does it say, “He heard”? It should have merely said “Yisroel came by the route of the spies and the Cannanite King of Arad came and attacked…” As the Torah writes (Shemos 17:8) “Amalek came and attacked Yisroel” and (Bamidbar 21:23) “[They] went out against Yisroel to the wilderness; he came to Yohatz and attacked Yisroel.” Similarly it says regarding Og (ibid. v. 33), “He came out against Yisroel, [he with all his people] to wage war at Edre’i.” Rather, it was because they heard that Aharon died and the Clouds of Glory departed. Furthermore one can answer that Rashi’s proof is from Parshas Masei (Bamidbar 33:40) where it is written, “The Canaanites heard…after Aharon’s death.” There it is clear that it was only because they had heard that Aharon had died and that the Divine Presence had departed from Yisroel. Rashi explains on that verse, “From here you learn…” The words, “From here” imply that he is explaining that his proof is from there, as I will explain there. Re’m explains: It is written above וַיִּרְאוּ כל העדה ["The entire community saw…"] (20:29) and Rabbi Abahu says (Rosh Hashanah 3a): Read this as וַיֵרְאוּ ["and they feared"] with a tzerei under the yud in accordance with Reish Lakish who says that here the word כי [translated in 20:29 as "that" but sometimes meaning "because"] comes to explain the matter that precedes it. [Consequently it means that they were fearful] since the community had become vulnerable because of Aharon’s death. It appears that this was why Rashi reversed the order of the verse and explained (20:29) “that [Aharon] had died” after “the entire community of Yisroel” in order to juxtapose it to the comment, “And the Canaanite heard.” R. Yaakov Triosh.
Or HaChaim
וילחם בישראל. He fought against Israel. The reason the Torah had to write the words בישראל, instead of עם ישראל as it did in Exodus 17,8 when Amalek is reported as attacking Israel, may be that in this instance the Israelites themselves were the cause that the Canaanites attacked them. They had sinned. The words: וישב ממנו שבי, "he took a prisoner from among them," the word ממנו suggesting that the reason Israel was attacked at this time was Israel itself. Israel's sin at this time was their share in causing the premature death of their High Priest Aaron on account of the events at "the waters of strife." Psalms 106,32 attributes G'd's anger to the people when the Psalmist exclaims: "they angered the Lord at the waters of Merivah and Moses suffered on their account." Naturally, David did not only refer to Moses but also to Aaron who shared in that mission. He singled out Moses by name as he was the principal involved.
Bartenura
חל להיות י"ד בע"ש, עיירות ומוקפין חומה קורין בו ביום – There is no Megillah reading on Shabbat, as a [rabbinic] preventive measure lest he take it [the Megillah] in his hand and he removes it four cubits into the public domain. And if one were to postpone the reading until after Shabbat, it would be the sixteenth [of Adar], and the Biblical verse (Esther 9:27), said: “ ולא יעבור /in the manner prescribed [and at the proper time each year].” But even though wall-city dwellers read the Megillah on the fourteenth [of Adar] when the fifteenth [of Adar] occurs on Shabbat, nevertheless, we don’t read [the portion] (Exodus 17:8 and following): “Amalek came [and fought with Israel at Rephidim]…” other than on Shabbat which is the fifteenth day [of Adar], and we recite the Haftarah of (I Samuel 15:2-31): “[Thus said the LORD of Hosts:] I am exacting the penalty [for what Amalek did to Israel, for the assault he made upon them on the road, on their way up from Egypt (and following)].” And [further] we discuss and expound the laws of Purim on that Sabbath. And regarding the Festive Purim meal, there are those who say that we do it on the fourteenth day [of Adar] when for on it we read the Megillah; and there are those who say that we postpone it until after Shabbat. And this is implied in the Jerusalem Talmud, that the Festival Purim meal that occurs on Shabbat is postponed but not advanced [to an earlier date], and according to everyone, we don’t do it on Shabbat.