Rashi: It is our relative (refer to 2:1:1:1, 2:1:1:1 ¹ ).

Malbim: It is a close, beloved relative - not a distant brother. Even though Na'ami's relative was rich, she did not ask him to feed her. She preferred that her daughter-in-law take Matanos Aniyim, 'gifts from Hashem.' It would be shameful to reveal to him her poverty, for he knew her when she was rich. Also, she hoped that he would redeem the field and Rus.

Torah Temimah citing Chulin 91a: A Chacham should not go out alone at night. (He will stay in the granary. He would not go out alone at night.)

Rashi: The generation stole wantonly. He will sleep there to guard his granary.

Malbim: The granary was at the end of the field. They did not winnow in the granary, rather, in the field in front of the granary. Surely all the male and female workers are there. When Rus comes to there, surely they will see her. This is not a problem, for they know that you are a relative. They will say that you came to see the success of your relative, or to see the girls, whom you did not see since the harvest ended.