In Acts 20, Paul is preaching to the elders of Ephesus. He states:

Act 20:35 I have shown you in every way, by laboring like this, that you must support the weak. And remember the words of the Lord Jesus, that He said, ‘It is more blessed to give than to receive.’ ”

This quote is not found in any of the four gospels (Matthew, Mark, Luke, and John). Either Paul was quoting oral tradition, quoting a disciple who knew Jesus, or quoting from his own appearances (visions) with Jesus. Alternatively, some have suggested a “Sayings Gospel” being circulated in the early church. I don’t think there is evidence to support that belief.