This is another story of a sincere offering that resulted in endless merit. The story is called "Nanda's Lamp Offering":
While the Buddha was residing at the Jetavana Monastery in Sravasti, tens of thousands of people would come everyday to listen to the Dharma. They would bring along with them all sorts of clothing and food to offer to the sangha. There was a poor, lonesome woman named Nanda who frequently came to listen to the Buddha's teachings. She was saddened when she saw the king, his minister, and the rich all make such fine offerings, and she knew that she would never be able to do the same. "How can a poor person like me, having to beg for every single meal, have anything to offer to the Buddha?
Then she recollected a saying she had heard, "If you wish to know the causes set up in your previous lives, you only need look at the results in your present life. Who is to blame for Nanda's desperate situation? Nanda, who thoroughly understood this lesson of the Dharma, knew that she could alter her grinding poverty only through making offerings and giving alms. She also realised that with wisdom, she could find a way to accumulate merit and attain liberation from suffering.
The next day, Nanda was very happy because she received an old piece of cloth while begging. She traded the cloth for a copper piece and bought an oil lamp to make an offering of light to the Buddha.
Nanda's wish to make an offering to the Buddha was realised when she lit the lamp and placed it before the Buddha. As she joined her palms and prostrated herself in front of the Buddha, she pronounced these words with utmost sincerity, "May the brightness of this lamp rid me of the ignorance which has been with me for many lives, may this light eradicate my bad karma, and provide me with great wisdom. Lord Buddha, please bless me with your compassion!"
Numerous lamps were laid in front of the Buddha by the many people praying for their own futures. Before dawn the next day, Maudgalyayana went to check the lamps. He found the lamps offered by the king and ministers were dim and dying out. The lamp from Nanda, however, was glowing extraordinarily brightly and the wick seemed unused. After daybreak, Maudgalyayana began to snuff out the lamps with a fan. While the other lamps died out, Maudgalyayana could not put out Nanda's lamp, no matter how he tried. Puzzled, he rushed to the Buddha for an answer. The Buddha explained, "Not only can Nanda's lamp not be put out by your fan, even if you were to splash it with all the water from the four great seas or blow at it with great gusts of wind, it would never be extinguished. This is because the owner of the lamp offered it with bodhi mind. Maudgalyayana, if one offers with arrogance or in an attempt to attract fame, the merit it creates is bound to be minimal. Regardless of how many material things one offers, offerings made with a self-serving attitude can only create limited merit."
At that time, Nanda again came to pay homage to the Buddha. The Buddha kindly stretched out his hand and gently touched her head as he prophesized, "In a future asamkhya kalpa, you will become a buddha by the name of Bright Lantern and will be honoured with ten different buddha titles." Nanda then renounced her household life and joined the sangha as a bhikshuni.
When the many devotees who were present heard what the Buddha had just said, they joyfully vowed to uphold the teachings and to be generous in almsgiving, thus lighting up bodhi lamps within themselves in offering to the Buddha.
(from Venerable Master Hsing Yun, "Traveling to the Other Shore")