וּשְׁאַבְתֶּם־מַ֖יִם בְּשָׂשׂ֑וֹן מִמַּעַיְנֵ֖י הַיְשׁוּעָֽה׃
你們必歡歡喜喜地從拯救的泉源打水。
Ibn Ezra
And you will draw water. By this figure the prophet indicates that they will rejoice exceedingly, as the thirsty rejoices when he draws water.
Rashi
from the fountains of the salvation For their heart will be dilated through the salvation that came to them, and secrets of the Torah that have been forgotten during the exile, because of the troubles, will be revealed to them.