It is narrated from Ibn Umar that the Prophet Muhammad (Blessings of Allah and Peace be upon him) said: "There aren't any days greater, nor any days in which deeds done in them are more beloved to Allah, the Most High, than these ten days (of Dhul-Hijja). So, increase in them the saying of Tahleel (La Ilaaha illa Allah), and Takbeer (Allahu Akbar) and Tahmeed (al-Hamdu lillah)" [Musnad Imaam Ahmad]
The Types of Deeds in These Ten Days:
Al-Baqara (The Cow) Sura 2: Verses 275-276
Those who devour usury shall not rise but as one who blunders through being affected by Satan, for they say, "Buying and selling is like usury," while God had made buying and selling lawful and prohibited usury. Hence, whosoever receives [positively] his[/her] Lord's admonition and gives over, he may keep his past gains, and it will be for God to judge him[/her], but whosoever returns to it, they are destined for the fire, therein to abide. God blots out usury, whereas He augments charitable offerings with fruitfulness [from various angles], and God loves not any ingrate and persisting evil-doer.