Paul reminded the Ephesian elders that Jesus said it is more blessed to do what?

Answer: Give than to receive

Paul quoted the Lord Jesus: "It is more blessed to give than to receive." This saying of Jesus is recorded only here.

“In everything, I showed you that by this kind of hard work we must help the weak, remembering the words of the Lord Jesus Himself: ‘It is more blessed to give than to receive.’””— Acts 20:35 (BSB)