He passed by the Euphrates while he was fasting, scooped up a small sip, drank it, and thereby broke his fast.
Recorded by Ibn Abī Shaybah (2/151/1) with a sound chain. He also transmitted it (2/151/2), and al-Bayhaqī did as well (4/247), through another, abridged chain that is likewise sound.
6 – 7. On the authority of Saʿīd al-Musayyab and al-Hasan al-Baṣrī, both said: “He may break his fast if he wishes.”
Ibn Abī Shaybah recorded this immediately after the previous report, and its chain is sound.
In another narration from al-Hasan al-Baṣrī: “He may break his fast in his house on the day he intends to set out,” cited by al-Qurṭubī in his Tafsīr (2/279).
In conclusion, a ḥadīth of this sort is supported by the Quran, the Sunnah, and authentic reports from the early generations—including some of the Rightly Guided Caliphs.1