四世祖吴福（945—1025）勤俭持家，有古之君子风范。闽商颜氏曾将数万钱寄放在吴家。久之，未取，吴福转借乡人，兼施济困，获息颇丰。多年后，颜氏来取，吴福将万缗本息全数奉还。颜氏不取利息，吴福辞让，两不能决。郡守命本归颜氏，平分利息。吴福力辞不取，遂将息钱捐给了天宁寺。
The fourth ancestor Wu Fu (945-1025), was praised for being industrious and thrifty. He was a good manager of the household and had the refined manners of an ancient gentleman. Once a merchant named Yan from Fujian Province deposited several thousand taels of silver in the Wu family house. The merchant did not demand the money back for a long time, so Wu Fu lent it to poor villagers, donated money for charitable works, and even obtained a handsome profit from the capital. Many years later, when the merchant came to take the money back, Wu Fu gave him both the principal and the interest. However, the merchant Yan respectfully declined to take the interest, and in the end the two turned to the local judge for a decision. The judge decided that the merchant should take the principal and that the interest should be divided equally between the two men. However, Wu Fu again refused to take his portion and donated it to the Tianning Temple.