$$3Ba^{2+}_{(aq)}+ 2H_3 PO_{4(aq)} \rightarrow Ba_3(PO_4)_{2 (s)}+ 6H^+_{(aq)}$$
In this reaction, barium ions and hydroxide ions from barium hydroxide react with hydrogen ions and phosphate ions from phosphoric acid to form barium phosphate, a solid compound, and water.
