"Give me back my strength"
The full line in the aria is: "Deh, tu, reggi, o Nume, il mio dolore" (roughly, "Oh, God, give me strength to bear my sorrow"). The line is part of Amneris' emotional plea to the gods as she wrestles with the pain of losing her love, Radames, to Aida, an Ethiopian slave.
The phrase "Deh Tu Reggi" is a powerful one, conveying Amneris' desperate need for support and strength in the face of her heart's shattering.