Ibn Abbaas, may Allah be pleased with him, reported that the Prophet (sallallaahu alaihi wa sallam) said: There are no days during which good deeds are more beloved to Allah than these days; meaning the first ten days of Dhul-Hijjah. They inquired: Not even Jihad in the cause of Allah? He said: Not even Jihad in the cause of Allah, unless one goes out for Jihad sacrificing both his life and property and returning with neither. (Al-Bukhaari)

Reading Material:
http://islamqa.com/en/ref/49042
http://islamqa.com/en/ref/1699
http://islamqa.com/en/ref/41633

Bilal Dannoun on Dhul Hijjah
http://kalamullah.com/Various%20Lectures/dhul_hijjah.mp3