Sayyiduna Samurah (may Allah be pleased with him) says: The Messenger of Allah (peace and blessings be upon him) forbade us from wisal in the month of fasting; he (peace and blessings be upon him) disliked it, but it was not a binding command.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6982