Let [the tribe of] Reuben live, and not die out, but let his men be few.
The earlier Bible translators could not believe that Moses meant to say of Reuben, “let his men be few,” so they put “not” in it in italics: “let ‘not’ his men be few.”
But Reuben had committed a grave offence [Genesis 49:3-4], which canceled his birthright, and God meant exactly what He directed Moses to say, as continuous fulfillment of the prophecy proves.
“In Judges 5:16 the tribe [of Reuben] is scorned for its failure to join the others against the Canaanites, and except for 1 Chronicles 5:3-20 it does not again appear in Israel’s history. Nor does Misha of Moab, ninth century, B.C. name it.” [Cambridge Bible].
Furthermore, by 1951 A.D. no Jew was permitted to enter the territory once allotted to the tribe of Reuben.
“The whole territory, which is … quite capable of cultivation, is now deserted by its settled inhabitants” [Davis’ Bible Dictionary]. It was then being restored, not by Israelites, but by Arabs.
– Amplified Bible: page 255