וְזֶה־לְּךָ֣ הָא֗וֹת אֲשֶׁ֤ר יָבֹא֙ אֶל־שְׁנֵ֣י בָנֶ֔יךָ אֶל־חָפְנִ֖י וּפִֽינְחָ֑ס בְּי֥וֹם אֶחָ֖ד יָמ֥וּתוּ שְׁנֵיהֶֽם׃
And this shall be the sign unto thee, that which shall come upon thy two sons, on Hophni and Phinehas: in one day they shall die both of them.
Read Kabbalistic (mystical) interpretations of I Samuel 2:34: Zohar and classical Jewish mystical sources, free online.