What should you do in the first 10 days of Zul-Hijjah?

سُـبْحٰـنَ الـلّٰــه You have heard the extent to which the first 10 days of Zul-Hijjah are full of blessings and mercies, in which the mercy of Allah Almighty descends in abundance upon the bondsmen. Whichever fortunate individual is successful in keeping fasts from the 1^st of Zul-Hijjah to the 9^th of Zul-Hijjah for the sake of Allah Almighty, Allah Almighty gives him the reward equivalent to freeing thousands of slaves, sacrificing (performing Ritual animal sacrifice of) thousands of camels, and giving thousands of horses in the way of Allah Almighty.

O Devotees of the Prophet! Just think! If this is the reward attained for keeping a single fast within these blessed days, then what would be the reward for the fortunate Muslim who spends these days performing different types of worship like fasting in the day and worshipping in the night, and who can imagine the various bounties Allah Almighty will bestow him with?! Therefore, do not by any means spend these 10 days in negligence. We should busy ourselves in worship and we should fast on every day except for the 10^th of Zul-Hijjah, as it is Makruh Tahreemi and a sin to fast on the 10^th of Zul-Hijjah. (Bahar-e-Shari’at, vol. 1, pp. 967, summarised; Durr-e-Mukhtar, vol. 3, pp. 391, summarised)

O Devotees of the Prophet! There are countless religious and worldly benefits of keeping Nafl fasts and the reward for them is so immense that one feels like devoting oneself to fasting continuously. For example, protection of one’s Iman, salvation from the Hell-fire, attaining of Paradise, saving money and time which is spent on eating within the daytime by fasting, keeping the stomach healthy, and protection from numerous amounts of illnesses. The greatest benefit is that Allah Almighty becomes pleased with the fasting person, thus we should attempt to keep some fasts every month, especially on Mondays, Thursdays and on Ayyam-ul-Bid’ (meaning the 13^th, 14^th and 15^th date of every Islamic month) as it is also a Sunnah to do so.

Umm’-ul-Mu’mineen Sayyidatuna Aaishah Siddiqah رَضِىَ اللهُ عَـنْهَا states: The Messenger of Allah صَلَّى اللهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم would fast on Mondays and Thursdays. (Tirmizi, vol. 2, pp. 186, Hadees 745, summarised)