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Diligence is steadfast application, assiduousness and industry; the virtue of hard work. It is one of the seven heavenly virtues.
Bernard et al. suggest diligence in a student is defined as an effort he or she puts towards balanced and holistic development in mental, physical, social and spiritual dimensions. They find diligence in students is correlated with academic performance. This is especially found in younger students. The support of parents and educators encourages students to be diligent. Other factors which encourage diligence in students include motivation, discipline, concentration, responsibility and devotedness.
The last words of the Buddha was "Strive on with diligence". Diligence is an integral part of all Buddhist teaching, and is considered the fourth of the pāramitā. In Mahayana tradition diligence is the third pāramitā and the first which is said to lead to liberation. The practice of diligence will bring an increase of qualities.
Diligence, in Christianity, is the effort to do one's part, while keeping faith and reliance in God. In other words, diligence and faith are two sides of a mystery. One doesn’t know how, despite one's effort, it all works out. But diligence when combined with faith assures spiritual success. Diligence as one of seven virtues describes thoroughness, completeness and persistence of an action, particularly in matters of faith.
We want each of you to show this same diligence to the very end, in order to make your hope sure. We do not want you to become lazy, but to imitate those who through faith and patience inherit what has been promised.—The Bible, 
That man can have nothing but what he strives for; That (the fruit of) his striving will soon come in sight: Then will he be rewarded with a reward complete.—The Quran, 
According to Brian Hatcher, the precepts of Hinduism require a human being to discover and live a dharmic life. To live a dharmic life, one must live with right intention with diligence, and with concern for well being of others. The Hindus celebrate Diwali, a festival of lights, where Goddess Lakshmi (also called Goddess Sri) is worshipped; the goddess symbolizes thorough preparation, being organized, diligent and honest. These characteristics are considered by Hindus as essential for success and Shubh Labh (ethical profit).
Who so performeth - diligent, content - the work allotted him, whatever it be, lays hold of perfectness!— The Bhagavad-Gita 18:45, 
Due diligence is the necessary amount of diligence required in a professional activity to avoid being negligent. This commonly arises in major acquisitions where the legal principle of caveat emptor (let the buyer beware) requires the purchaser to make a diligent survey of the property or service.