Musannaf Ibn Abi Shaybah

12902 - Hushaym narrated to us from Yunus from al-Hasan regarding a man who made fasting (a month) obligatory upon himself (1), he said: (If) (2) he specified a known month, then let him fast it (and consecutively) (3), and if he did not (specify) (4) a known month (or) (5) did not intend it, then let him begin the days and fast thirty days, (for if) (6) he fasted according to (7) the crescent and broke his fast upon its sighting and it was twenty-nine (days) (8), that suffices him, and if he separated (if) (9) he began the days.

Hazrat Abu Qalabah says that if a person says, "I have fasts of one month upon me," then he knows best what he has said, and his intention is to be considered (it will be based on his intention).

Hazrat Hammad and Ibrahim state that if a person makes a vow that he has to fast for one month, and does not specify any particular month, then if he wishes, he may fast consecutively, and if he wishes, he may fast on separate days.

12905 - And from (Hammad) (1) from Ibrahim (they said) (2): If a man makes fasting a month obligatory upon himself and does not specify (3) a particular month, he said: If he wishes, he may fast consecutively, and if he wishes, he may separate (the days).

Hazrat Maymoon says that if the vow is of fasting, then they will be observed consecutively.

Hazrat Hajjaj says that I asked Hazrat Ata, and the person who had asked Ibrahim told me: If a person makes a vow that he must fast for a month, both said: He will fast thirty days, that is, it is not necessary to keep them consecutively.