וּבְפָרִשְׂכֶ֣ם כַּפֵּיכֶ֗ם אַעְלִ֤ים עֵינַי֙ מִכֶּ֔ם גַּ֛ם כִּֽי־תַרְבּ֥וּ תְפִלָּ֖ה אֵינֶ֣נִּי שֹׁמֵ֑עַ יְדֵיכֶ֖ם דָּמִ֥ים מָלֵֽאוּ׃
And when ye spread forth your hands, I will hide Mine eyes from you; Yea, when ye make many prayers, I will not hear; Your hands are full of blood.
Read Jewish philosophy on Isaiah 1:15: Rambam's Guide for the Perplexed, Saadia Gaon, and classical Jewish philosophical sources, free online.