The Buddha uses similes of a building with a peaked roof, fragrances, and regional kings to illustrate the importance of diligence in developing the Noble Eightfold Path.

Kūṭādi sutta - Beginning with Peak

45.141

"Bhikkhus, just as the rafters of a building with a peaked roof all slope towards the peak, incline towards the peak, and meet together at the peak, so too, bhikkhus, whatever wholesome qualities there are, they all slope towards diligence, incline towards diligence, and meet together in diligence; diligence is considered to be the foremost among the qualities. For a diligent bhikkhu, this is to be expected - that he will develop and extensively cultivate the Noble Eightfold Path.

And how, bhikkhus, does a diligent bhikkhu develop and extensively cultivate the Noble Eightfold Path? Here, bhikkhus, a bhikkhu develops right view dependent on seclusion, supported by dispassion, based on ending, culminating in complete relinquishment; similarly he develops right intention, right speech, right action, right livelihood, right effort, right mindfulness, and right collectedness, dependent on seclusion, supported by dispassion, based on ending, culminating in complete relinquishment. It is in this way, bhikkhus, that a diligent bhikkhu develops and extensively cultivates the Noble Eightfold Path."

45.142

"Bhikkhus, just as whatever root fragrances there are, all of them are overshadowed by the kāḷānusāriya fragrance; kāḷānusāriya is considered to be the foremost of them because of its superior intensity. In the same way, bhikkhus, whatever wholesome qualities there are, they are all rooted in diligence and meet together in diligence. Diligence is considered the foremost among the qualities. For a diligent bhikkhu, this is to be expected - that he will develop and extensively cultivate the Noble Eightfold Path."

45.143

"Bhikkhus, just as whatever heartwood fragrances there are, all of them are overshadowed by red sandalwood; red sandalwood is considered to be the foremost of them because of its superior intensity. In the same way, bhikkhus, whatever wholesome qualities there are, they are all rooted in diligence and meet together in diligence. Diligence is considered the foremost among the qualities. For a diligent bhikkhu, this is to be expected - that he will develop and extensively cultivate the Noble Eightfold Path."

45.144

"Bhikkhus, just as whatever flower fragrances there are, all of them are overshadowed by jasmine; jasmine is considered the foremost of them because of its superior intensity. In the same way, bhikkhus, whatever wholesome qualities there are, they are all rooted in diligence and meet together in diligence. Diligence is considered the foremost among these qualities. For a diligent bhikkhu, this is to be expected - that he will develop and extensively cultivate the Noble Eightfold Path."

45.145

"Bhikkhus, just as whatever regional kings there are, all of them follow the wheel-turning monarch; the wheel-turning monarch is considered the foremost of them. In the same way, bhikkhus, whatever wholesome qualities there are, they are all rooted in diligence and meet together in diligence. Diligence is considered the foremost among these qualities. For a diligent bhikkhu, this is to be expected—that he will develop and extensively cultivate the Noble Eightfold Path.

And how, bhikkhus, does a diligent bhikkhu develop and extensively cultivate the Noble Eightfold Path? Here, bhikkhus, a bhikkhu develops right view dependent on seclusion, supported by dispassion, based on ending, culminating in complete relinquishment; similarly he develops right intention, right speech, right action, right livelihood, right effort, right mindfulness, and right collectedness, dependent on seclusion, supported by dispassion, based on ending, culminating in complete relinquishment. It is in this way, bhikkhus, that a diligent bhikkhu develops and extensively cultivates the Noble Eightfold Path."