Commentary for Berakhot 86:14

ואל יצא יחידי בלילה משום חשדא ולא אמרן אלא דלא קביע ליה עידנא אבל קביע ליה עידנא מידע ידיע דלעידניה קא אזיל

He should not go out alone at night, because of the suspicion [it may arouse] ; and they mean only where he has no fixed hour [for going out at night], but if he have a fixed hour, it will be well known that he goes out as is his usual custom.

Abraham Cohen Footnotes to the English Translation of Masechet Berakhot