How Might One Obtain Ikhlaas? - by Imām Ibn Qayyim al-Jawziyyah Ikhlaas
cannot coexist in a heart which [embraces] the love of praise and
commendation, [nor] the yearning [to obtain] that which is possessed
amongst the people, save in the [manner] that fire and water, or a
lizard and fish may coexist.
Ikhlaas - Based on Sh. Husayn al-Awaayishah's "Book of Sincerity"
 How does one Attain Sincerity? - troid.ca A
brief excerpt from Imaam Ibnul-’Uthaymeen’s explanation of
Riyaadus-Saaliheen demonstrating the importance of sacrifice as a means
to attain piety and sincerity.
The Hadeeth of Intention - Imaam Ibn Rajab al-Hanbali
Ibn Rajab provides an excellent explanation of the niyyah from the well
known hadeeth of 'Umar ibn al-Khattaab. Many statements from the Salaf
and additional hadeeth texts
The Acceptable Action - From Hussain Al-Awaa'ishahs Kitaab Ul-Ikhlaas - Abu Iyaad Stressing
the importance of correct intention and actions conforming to the Book
and the Sunnah and how they are two conditions for the acceptable action