Because the SEH, (Lamb, SHEMOT 12:3; YESHAYAH 53:7 Moshiach) at the center of the Kes (Throne), will shepherd them and will lead them to the Makor Mayim Chayyim ["Fountain, source of Living Waters," YIRMEYAH 2:13], and Hashem will wipe away every tear from their eynayim. [YESHAYAH 25:8; 35:10; 51:11; 65:19]