H^- is a

Lewis bases are those bases that can donate electron pairs to an electron-deficient compound or the compound which acts as an electron acceptor. A Bronsted base is a base that can accept a proton from a Bronsted acid or proton donor. Therefore, the Bronsted base is also known as a proton acceptor. Hydride ion acts as both Lewis acid and Bronsted base.

$$\begin{gathered} {\mathrm{AlH}}_3+{\mathrm{H}}^{-}\to {\mathrm{AlH}}_4^{-} (\mathrm{Lewis} \mathrm{acid}) \\ {\mathrm{H}}^{-}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_2+{\mathrm{OH}}^{-} (\mathrm{Bronsted} \mathrm{Base}) \end{gathered}$$