This teaching is from the section The Four Noble Truths - The Matrix of the Teaching from "Noble Truths, Noble Path" by Bhikkhu Bodhi.

The Buddha explains the urgency of understanding the Four Noble Truths to end suffering with a simile of extinguishing a fire on one's clothes or head.

"Bhikkhus, if one's clothes or head were burning, what should be done?

"Venerable sir, if one's clothes or head were burning, then should arouse the utmost intention (wish, desire, interest [chanda]), make an extraordinary effort, stir up perseverance, enthusiasm, tireless determination (indefatigably, resolute intention [appaṭivānī]), and apply mindfulness [1] and full awareness (clear comprehension [sampajañña]) should be applied to extinguish the burning of one's clothes or head."

Bhikkhus, even though one's clothes or head were burning, one might look on equanimously, paying no attention to it. But as long as one has not made the breakthrough to the Four Noble Truths as they really are, then in order to make the breakthrough, one should arouse the utmost intention, make an extraordinary effort, stir up perseverance, enthusiasm, tireless determination, and apply mindfulness and full awareness.

And what are these four? The Noble Truth of suffering [2], the Noble Truth of the arising of suffering [3], the Noble Truth of the ending of suffering [4], the Noble Truth of the way of practice leading to the ending of suffering [5].

Therefore, bhikkhus, effort should be made to fully understand (understand in principle, then discern in each moment and then experientially penetrate): 'This is suffering';

effort should be made to fully understand: 'This is the arising of suffering';

effort should be made to fully understand: 'This is the ending of suffering';

effort should be made to fully understand: 'This is the way of practice leading to the ending of suffering.'"

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[1] mindfulness = observing the body in and of itself, felt experience in and of itself, mind in and of itself, mental qualities in and of themselves [sati]

[2] suffering = mild or intense suffering, discomfort, pain, disease, unpleasantness, stress, discontentment, dissatisfaction [dukkha]

[3] arising of suffering = source of stress, appearance of discomfort [dukkhasamudaya]

[4] ending of suffering = ending of discontentment, cessation of distress [dukkhanirodha]

[5] way of practice leading to the ending of suffering = the noble eightfold path [dukkhanirodhagāmī]

Related Teachings:

Ethics, confidence, diligence precede the eightfold path (SN 46.50 - 54) - As the dawn precedes the sun, ethics, enthusiasm, confidence, right view, and diligence precede the eightfold path.

The effects of cultivating the eightfold path are gradual (DhP 273) - This post has linked teachings for diving further into each factor of the noble eightfold path.