The fourth son of Jacob by Leah (Gen. Gen. 29:35). Judah means praise (Gen. Gen. 29:35) and was in the line leading to the Messiah and led the procession of the tribes (Num. Num. 10:14), even into battle (Jdg. Jdg. 20:18 cf. 2Chr. 2Chr. 20:21; Ps. Ps. 149:6). See Camp of Israel. See commentary on Revelation 5:5.
twelve thousand were sealed
The number twelve in the Scripture has a special association with the idea of completion and it is also attached inseparably to the destiny of Gods chosen earthly people, Israel. Immediately, of course, we think of the twelve tribes and the twelve apostles.1 See Twelve: Jewish Tribes, Completeness.
the tribe of Reuben
The first son of Jacob by Leah (Gen. Gen. 29:32). Reuben means see ye a son.
the tribe of Gad
The seventh son of Jacob by Leahs handmaid, Zilpah (Gen. Gen. 30:11). Gad means a troop.