144,000 are sealed, 12,000 from 12 tribes of Israel (Revelation 7:4-7). Those are consecrated for martyr sacrifice.

Immediately John sees a great multitude from every tribe and tongue and nation and people (7:9), holding palm branches.

It reminds one of Elim, with its 12 springs and 70 palm trees (Exodus 15). The 144,000 martyrs become the springs of living water that give life to the palm trees of the nations.