Virtue of the first ten days of Dhil-Hijja:

Dear brothers, among the great blessings from Allah to His good servants are the occasions for worship and increasing good deeds. One of these occasions are the ten days of Dhil-Hijjah.  

The virtue of these ten days is referred to in the Qur’an and Sunnah. Allah says, 

((By the dawn; By the ten nights ))

[Al-Fajr, 1-2]

 Ibn Kathir said, "Those ten nights mentioned in the ayah are the first ten days of Dhil-Hijjah.")). Ibn Abbas said the same.
 Dear brothers,
 Ibn Abbaas, may Allah be pleased with him, reported that the Prophet (PBUH) said,

"There are no days during which good deeds are more beloved to Allah than these days; meaning the first ten days of Dhil-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 returns with neither."

[Al-Bukhari]

 Listen again to what Allah says,

(By the dawn; By the ten nights)

 Allah refers to these ten days in another ayah, saying,

((And mention the Name of Allah on appointed days) )

[Al-Hajj, 28]

 Ibn Abbas said, "They are the first ten days of Dhul-Hijjah."