All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallAllaahu ‘alayhi wa sallam, is His Slave and Messenger.
We could not find the Hadeeth to which you referred in the Hadeeth books and references; however, Imaam Al-Qurtubi cited in his book At-Tathkirah bi Ahwaal Al-Mawta wa Umoor Al-Aakhirah a Hadeeth in this relation, quoted from Imaam Abu Haamid Al-Ghazaali, but he did not mention the Hadeeth's chain of narration or the source in which it was cited.
Al-Qurtubi wrote: "Abu Haamid Al-Ghazaali mentioned in his book Kashf 'Ilm Al-Aakhirah that a man will be brought on the Day of Judgment with his good and bad deeds of equal weight and no good deed to tip his scale of good deeds. So Allaah The Exalted will say to him from His mercy: 'Go and see if anyone gives you one good deed by which I will admit you to Paradise.' The man will go through the people and whenever he asks someone to give him one good deed, everyone will refuse and say, 'I fear that my scales will be lighter. I need it more than you.' He will despair, and then a man will say to him: 'What do you seek?' He will reply, 'One good deed; I have passed people who have a thousand good deeds, but they have not given me any.' The other man will say, 'I have met Allaah The Exalted and did not find except one good deed in my record (of good deeds). I do not believe that it will avail me in the least; take it as a gift from me to you!' Joyfully, the man sets off and Allaah says to him, 'What have you done?' and He knows best. The man will reply, 'Such a thing happened!' Allaah The Exalted will call the other man who gave him the good deed and say to him, 'My generosity is vaster than yours; take your brother by the hand and enter Paradise together.'"
It is well-known that a report is not classified as Saheeh or Hasan except after investigating its chain of narration and verifying that all the conditions to classify it as Saheeh or Hasan are met. A report is not affirmed as Saheeh or Hasan merely because it is attributed to the Prophet, sallallaahu ‘alayhi wa sallam.
Allaah Knows best.