'Wells' speak of abundance, satisfaction and refreshing for the thirsty heart. cp. Isa 55:1; Joh 4:10; Rev 21:6
This prophecy (v.3) speaks of the fulfillment of the feast of Tabernacles, for in His Millennial Kingdom, the Lord will dwell among His people (v.6).
In the days of the second Temple, during the celebration of the feast of Tabernacles, the priests would draw water from the pool of Siloam, carry it to the Temple, and pour it out at the altar as they recited v.3. That was the occasion of Jesus' words in Joh 7:37-39. (See the Book Notes at John 7:37-39.)
Salvation is the saving of a soul from death (see Rom 6:23).
The 'water of life' must be drawn from a well of inexhaustible, eternal life. There is only One such well: the LORD JEHOVAH who has become our Yeshua. cp. Joh 4:14; 5:24-27; 8:58; 10:30; 11:25,26; 17:3; Rev 22:1,16-17
(7.) The King: His Praise, the song of all people (12:4-6)
4. And in that day shall ye say, Praise the LORD, call upon his name, declare his doings among the people, make mention that his name is exalted.
5 Sing unto the LORD; for he hath done excellent things: this [is] known in all the earth.
6 Cry out and shout, thou inhabitant of Zion: for great [is] the Holy One of Israel in the midst of thee.