Lewis & Short

Săūl, ūlis, or indecl. m., the first king of the Jews, Alcim. ad Sor. 435; Paul. Nol. Carm. 13, 601; Vulg. 1 Reg. 9, 2; id. Act. 13, 21; gen. Saulis, id. Isa. 10, 29; dat. Sauli, id. Psa. 51, 1; acc. Saulem, id. 1 Reg. 15, 35.