Midrasch zu Rut 1:12

“Turn back, my daughters, go, as I am too old to be with a husband. If I were to say: I have hope, even were I to be with a husband tonight, and also were I to bear sons” (Ruth 1:12).
“Turn back, my daughters, go” – Rabbi Shmuel bar Naḥmani said in the name of Rabbi Yudan bar Rabbi Ḥanina: In three places it is written here: “Turn back” (Ruth 1:8), “Turn back” (Ruth 1:11), “Turn back” (Ruth 1:12), corresponding to the three times that one rejects a convert. If he insists beyond that, one accepts him. Rabbi Yitzḥak said: “A stranger shall not stay the night outside” (Job 31:32). A person shall always reject with the left and accept with the right.¹¹³Rejection should be performed weakly, while the subsequent acceptance should be undertaken powerfully. “As I am too old to be with a husband […were I to be with a husband tonight]” – Rabbi Yoḥanan said: The Torah teaches you proper conduct, that one engages in marital relations at night and not by day. That is what is written: “In the evening she would come and in the morning she would return” (Esther 2:14), and it is written: “Were I to be with a husband tonight.”