There's a famous story that, eventually, the Buddha vowed not to move until he gained enlightenment.
The story can be found for example here:
Still seeking a way to understand the meaning of life, Siddhartha set out for Buddhagaya. Near a grove, he sat down under a huge Bodhi tree. Silently he vowed, "Even if my flesh and blood were to dry up, leaving only skin and bones, I will not leave this place until I find a way to end all sorrow." He sat there for forty nine days. He was determined to discover the source of all pain and suffering in the world. Mara, the evil one, tried to scare him into giving up his quest. For instance, he hoped to lure Siddhartha into having selfish thoughts by sending visions of his very beautiful daughters. But the Buddha's goodness protected him from such attacks.
And for example here:
One day, when his physical strength had returned, he approached a lovely spot in Uruvela by the bank of the Nerañjara River. Here he prepared a seat of straw beneath an asvattha tree (later called the Bodhi Tree) and sat down cross-legged, making a firm resolution that he would never rise up from that seat until he had won his goal. As night descended he entered into deeper and deeper stages of meditation until his mind was perfectly calm and composed. Then, the records tell us, in the first watch of the night he directed his concentrated mind to the recollection of his previous lives. Gradually there unfolded before his inner vision his experiences in many past births, even during many cosmic aeons; in the middle watch of the night he developed the "divine eye" by which he could see beings passing away and taking rebirth in accordance with their karma, their deeds; and in the last watch of the night he penetrated the deepest truths of existence, the most basic laws of reality, and thereby removed from his mind the subtlest veils of ignorance. When dawn broke, the figure sitting beneath the tree was no longer a Bodhisatta, a seeker of enlightenment, but a Buddha, a Perfectly Enlightened One, one who had attained the Deathless in this very life itself.
What is/are the original or canonical source[s] of this story?
Some suttas like the Maha-Saccaka Sutta (MN 36) are an account of that period of this life, but without mentioning the vow.