Why will Hashem ignore when you spread your hands?
Rashi: "Your hands are full of blood." Radak - how are you not ashamed, and spread to Me your hands full of blood?!
Malbim: Before, the Navi taught that good acts, i.e. bringing Korbanos and gathering in the Mikdash, will not help without good intent. Now he teaches that also good intent will not help if man is filthy with sinful acts. Pure Avodah requires Kedushah of action and intent.
Why does it mention Tefilah? Is this not spreading your hands?
Radak citing his father: Indeed, spreading the hands is Tefilah - "Efros Es Kapai El Hashem" (Shemos 9:29). (The matter is repeated in different words - PF.)
Radak (from Brachos 32b): Spreading the hands is Birkas Kohanim. A Kohen who killed someone is disqualified from this -- "Yedeichem Damim Male'u."
Malbim: Tefilah is pouring out the Nefesh with clear, proper intent. Even so, I cannot hear it, because "your hands are full of blood"!
