Esther 1:1
Now it came to pass in the days of Ahasuerus, (this is Ahasuerus which reigned, from India even unto Ethiopia, over an hundred and seven and twenty provinces:)
Cross-reference
In Esther 8:9, the same empire extent 'from India to Cush' appears, reinforcing the vast domain introduced in Esther 1:1.
Esther 2:3 shows the same 127 provinces in action as officers gather virgins for the king — direct narrative continuity.
Esther 4:3 shows the same provinces reacting to the edict to destroy the Jews — direct narrative continuity.
Esther 9:20 confirms the same provincial scope for Mordecai's letters establishing Purim.
Esther 9:30 explicitly mentions the 127 provinces of Ahasuerus — direct numerical echo of the opening verse.
Esther 10:1 continues the reign of Ahasuerus with his tribute — same historical context.
In Ezra 4:6, Ahasuerus is also named as the king who received an accusation against the Jews, linking to the same Persian ruler in Esther.