Rashi in his commentary to Genesis 7:7 writes:
אף נח מקטני אמנה היה מאמין ואינו מאמין שיבא המבול ולא נכנס לתיבה עד שדחקוהו המים
I see (at least) two ways to read this:
Noah believed in general (in God?) but did not believe the specific idea that a flood would come. (I.e. a comma after the first word מאמין.)
Noah believed-but-did-not-believe in the specific idea that a flood would come. (I.e. מאמין ואינו מאמין is one phrase meaning that he partially believed it, or he vacillated in his belief.)
Is there any evidence that one of these readings is (more) correct?
(I have seen some early Midrashic sources with the same idea, but they didn't use the specific wording of מאמין ואינו מאמין, so I don't know if any proof can be brought from them.)