Performing Hajj and ‘Umrah.
One of the best deeds that one can do during these ten days is to perform Hajj to the Sacred House of Allaah. The one whom Allaah helps to go on Hajj to His House and to perform all the rituals properly is included in the words of the Prophet (peace and blessings of Allaah be upon him):
“An accepted Hajj brings no less a reward than Paradise.”
Doing more good deeds in general, because good deeds are beloved by Allaah and will bring a great reward from Him. Whoever is not able to go to Hajj should occupy himself at this blessed time by worshipping Allaah, praying (salaat), reading Qur’an, remembering Allaah, making supplication (du’aa’), giving charity, honouring his parents, upholding the ties of kinship, enjoining what is good and forbidding what is evil, and other good deeds and acts of worship.
One of the good deeds that will bring a person closer to Allaah during these ten days is offering a sacrifice, by choosing a high-quality animal and fattening it, spending money for the sake of Allaah.
One of the most important things to do during these ten days is to repent sincerely to Allaah and to give up all kinds of disobedience and sin. Repentance means coming back to Allaah and foregoing all the deeds, open and secret, that He dislikes, out of regret for what has passed, giving it up immediately and being determined never to return to it, but to adhere firmly to the Truth by doing what Allaah loves.If a Muslim commits a sin, he must hasten to repent at once, without delay, firstly because he does not know when he will die, and secondly because one evil deed leads to another.