Looking for a Buddhist story about trust

The Story of King Pasenadi of Kosala

While residing at the Jetavana monastery, the Buddha uttered Verse (204) of this Dhammapada, with reference to King Pasenadi of Kosala.

One day, King Pasenadi of Kosala went to the Jetavana monastery after having his full morning meal. It was said that the king had eaten one quarter basket (about half a bushel) of rice with meat curry on that day; so while listening to the Buddha's discourse he felt very sleepy and was nodding most of the time. Seeing him nodding, the Buddha advised him to take a little less rice everyday and to decrease the amount on a sliding scale to the minimum of one-sixteenth part of the original amount he was taking. The king did as he was told and found that by eating less he became thin, but he felt very much lighter and enjoyed much better health. When he told the Buddha about this, the Buddha said to him, "O king! Health is a great boon; contentment is a great wealth; a close and trusted friend is the best relative; Nibbana is the greatest bliss."

Then the Buddha spoke in verse as follows:

Verse 204: Health is the greatest gift, contentment is the greatest wealth, a trusted friend is the best relative, Nibbana is the greatest bliss.

On the matter of trust in giving, there is the Dakkhiṇāvibhaṅga Sutta:

“When an ethical person with trusting heart gives a proper gift to unethical persons, trusting in the ample fruit of deeds, that offering is purified by the giver.

When an unethical and untrusting person, gives an improper gift to ethical persons, not trusting in the ample fruit of deeds, that offering is purified by the receivers.

When an unethical and untrusting person, gives an improper gift to ethical persons, not trusting in the ample fruit of deeds, I declare that gift is not very fruitful.

When an ethical person with trusting heart gives a proper gift to ethical persons, trusting in the ample fruit of deeds, I declare that gift is abundantly fruitful.

But when the passionless gives to the passionless a proper gift with trusting heart, trusting in the ample fruit of deeds, that’s truly the best of material gifts.”

I remember a very similar story in an episode of the TV series “Kung Fu” with David Carradine. 2 boys were robbed taking some goods to town: one of them was Kwai Chang Caine. One boy gave the response you quoted, whereas Caine said “Always be aware Master” and was allowed to remain in The monastery. It is possible the writers borrowed the story.

I have heard a similar story. But it's not exactly a Buddhist story. There is a book called 'Pancha Tanthra'. It has many stories like this. There are also youtube videos on these stories as cartoons. Try googling 'Pancha tantra stories about trust'. You will find many resources.

As another answer already said, it features in an episode of the old Kung Fu TV series -- see Season 1, episode 7, The Tide -- one of the footnotes says:

When the young Caine and another student are robbed, the other student learns not to trust strangers and is dismissed from the temple. Shaolin are required to trust: the TAO TE CHING [F] says in both chapters #17 and #23, "He who does not trust enough, will not be trusted."

I don't know about the quote from the Tao Te Ching -- I looked in a couple of translations and didn't see the cited quote in chapters 17 or 23.

In one translation I looked at, it does say in Chapter 49 ...

The saint trusts those who are trustworthy.
He also trusts those who are not trustworthy.
This is the true virtue of trust.

... but the Tao Te Ching isn't Buddhism, presumably.

Apparently Shaolin is Buddhist -- contrasted I thought with Wudang, which was or is Taoist -- but, I don't know, maybe Shaolin has Taoist influences too -- I doubt we can trust the Kung Fu TV series to be really accurate, culturally.

The Pali Canon has some good ones on the "Trust, but verify" theme, like the "Four Great References" in DN 16, the Gotami Sutta, or the famous Kalama Sutta of AN 3.65