The lines are an allusion to the Book of Revelations, more specifically the end of chapter 7 and the beginning of chapter 8:
[Chapter 7: 17] For the Lamb which is in the midst of the throne shall feed them, and shall lead them unto living fountains of waters: and God shall wipe away all tears from their eyes.
[Chapter 8: 1] And when he had opened the seventh seal, there was silence in heaven about the space of half an hour.
 And I saw the seven angels which stood before God; and to them were given seven trumpets.
 And another angel came and stood at the altar, having a golden censer; and there was given unto him much incense, that he should offer it with the prayers of all saints upon the golden altar which was before the throne.
(See BibleHub.com for alternative translations of Revelations 8:1.)
The song title "Rivers of Belief" refers to the role that rivers, sometimes sacred rivers, play in some religions. For example, Jesus was baptised in the river Jordan. For Hindus, the Ganges and the Yamuna are sacred rivers in India. While the song almost literally quotes the Bible, the line "I will return" can also be read as an allusion to reincarnation, which is a belief in Hinduism (among other religions).
The meaning of the seventh seal and the silence that follows its opening is a matter of Biblical hermeneutics. The Wikipedia article about the seven seals, for example, summarises five views: the preterist view, the historicist view, the futurist view, the idealist view and the Mormon view. The answers to the question In Revelation 8:1 does opening the seventh seal do anything? on Biblical Hermeneutics Stack Exchange present an additional set of interpretations. It seems that the meaning of that line remains open to debate.