http://www.torah.org/learning/tefilah/17thblessing.html The Seventeenth Blessing: Fires of Israel“Be favorable, Hashem, our G-d, toward Your people Israel and their prayer and restore the service to the Holy of Holies of Your Temple. The ‘ishei Yisrael’ and their prayer accept with love and favor.”The seventeenth blessing of Shemoneh Esrei begs Hashem to find the Jewish people and their service of Him favorable. Among the things that we ask Hashem to look favorably on are ishei Yisrael, which can be translated as either “the individuals of Israel” or the “fires of Israel.”
The second translation refers to the countless Jewish people throughout the ages who have lost their lives as a sanctification of G-d’s name, at the hands of oppressors who sought to wipe the Jews and the Torah off the face of the earth. Someone who is killed by fire, like Rabbi Chanina ben Tradion, is literally transformed into an ishei Yisrael, a human burnt offering (Pikudei Eliezer, as cited in the Leket Hakemach HaChadash).
Some explain that ishei Yisrael refers to the burnt offerings that were sacrificed in the Temple. A person bringing this offering was meant to recognize that, because of his transgressions, he deserved to be burnt up on the altar. When the person bringing the sacrifice understands that it is a substitute for himself, these burnt offerings are also considered ishei Yisrael (based on Gra 120,1, according to Tosfos Menachos 110a).
Ishei Yisrael can also refer to the souls of the Jewish people. The Medrash says that the angel Michael serves as the kohen gadol in the heavens, and after the righteous pass away, he brings their souls as a sacrifice before Hashem every day. We ask Hashem to favor the souls of these ishei Yisrael (Taz, according to Tosfos Menachos 110a).
All of the above explanations of ishei Yisrael share a common thread related to giving up something of ourselves to Hashem. Let us try to understand how each of the final blessings develops this theme.