Which tribe is listed first among those sealed in Revelation 7?

Answer: Judah

The list begins, "From the tribe of Judah 12,000 were sealed," followed by Reuben and Gad.

“And I heard the number of those who were sealed, 144,000 from all the tribes of Israel: From the tribe of Judah 12,000 were sealed, from the tribe of Reuben 12,000, from the tribe of Gad 12,000,”— Revelation 7:4-5 (BSB)