The Prophet (sallallahu alayhi wasallam), has clearly mentioned the importance and the virtue of these blessed days.
It is reported by Abdullah Ibne Abbaas (radhiyallahu anhuma) that the Prophet (sallallahu alayhi wa sallam) said, “No good deeds done on other days are superior to those done on these (first ten days of zil hijjah).
Thereupon, some companions of the Prophet (sallallahu alayhi wa sallam) said, “Not even Jihadd ? ”
He replied, “Not even Jihaad, except that of a man who does it by putting himself and his property in danger (for Allah’s sake) and does not return with any of these things.”
[Bukhaari Vol.1 pp.132]