Rabbi Elazar ben Dordia was a man consumed by desire. The Talmud in Tractate Avodah Zarah says there was not a single prostitute in the world he had not visited. When he heard about one who lived across the sea and charged a purse full of dinars, he crossed seven rivers to reach her.
During their encounter, she made a remark that shattered him. The exact words vary in different versions of the text, but the effect was the same: she told him that his repentance would never be accepted. He would never be able to return.
Rabbi Elazar ben Dordia went outside and sat between two mountains. He turned to the mountains and hills: "Pray for mercy on my behalf." They answered: "Before we can pray for you, we must pray for ourselves." He turned to the heavens and earth: "Pray for mercy on my behalf." Same answer. He turned to the sun and moon, the stars and constellations. Each refused. Each said they had their own problems.
Finally, he understood. "The matter depends on me alone."
He placed his head between his knees and wept. He wept and wept until his soul departed from his body.
At that moment, a heavenly voice declared: "Rabbi Elazar ben Dordia is destined for the World to Come."
When Rabbi Yehuda HaNasi—the editor of the Mishnah, the most authoritative rabbi of his generation—heard this story, he cried. He said: "There are those who acquire their share in the World to Come only after many years of service, and there are those who acquire it in a single moment."
The Talmud is making a radical claim. A lifetime of sin was overturned by a single act of genuine, bone-deep repentance. No mountains could help him. No stars could intervene. Teshuvah (תשובה), the act of returning, was his alone to perform. And it was enough.