Midrash Tanchuma
In the Book of Judges, it is written concerning Ehud: And Ehud made him a sword which had two edges (ibid. 3:16). This indicates that he would have a share in two worlds because he had studied the law, about which it is stated: A two-edged sword in their hand (Ps. 149:6). Hence he was privileged to enjoy the fruits of this world and the hereafter.