What was the significance of the twelve springs and seventy date-palms?
Rashi and Targum Yonasan: The twelve springs corresponded to the twelve tribes; 1 and the seventy date-palms to the seventy elders. 2
Ramban (citing Ibn Ezra): The Pasuk mentions it to stress the contrast between Elim, and the previous encampment in Marah where the water was bitter, 3 and date-palms do not flourish where the water is bitter.
Seforno: Even though the location was so convenient, they did not hesitate to move on when ordered to travel. 4
One for each tribe (Ramban and Targum Yonasan). Toras Avigdor (Beshalach, p. 2) - Hashem wanted each tribe to be independent. Similarly, we find (24:4) that Moshe built twelve Matzevos, one for each tribe.
Ramban: The seventy elders sat in the shade of the date-palms - all this in praise of Hashem, who miraculously prepared it for them from the day of the creation in an arid land.
Ramban: In fact it was because of the pleasant conditions that they remained there longer than most of the other encampments in the desert - as hinted in the words "va'Yachanu Sham."
Seforno: As Hashem stated in praise of Yisrael, "You followed Me in the desert" (Yirmeyah 2:20).
QUESTIONS ON RASHI
Rashi writes: "'Twelve springs' - they found there, corresponding to the twelve Tribes; 'And seventy date-palms' - corresponding to the seventy elders." Why not give a simple meaning - The Torah is emphasizing that at this new location, there was ample water to drink?
Gur Aryeh: Although 12 springs of water could conceivably have sufficed for 600,000 people, the dates of seventy palm-trees certainly did not suffice (by natural means)! Rather, the number of both the trees and the springs matched the number of Bnei Yisrael. Hashem was showing them how He planned this location for their arrival. According to the Mechilta, these features were located there ever since Creation.