Dr. Muhammad Siraj, professor of Islamic studies at the American University in Cairo (AUC), stated regarding this issue: “The majority of scholars do not stipulate that one should take witness for divorce. Divorce does count as soon as one pronounces it. However, the Shi`ah Imamiyyah stipulate taking witness for divorce. This means that divorce does not count unless there is witness to prove it.
This difference is related to the Qur’anic verse: “Thus when they fulfill their term appointed, either take them back on equitable terms or part with them on equitable terms; and take for witness two persons from among you, endued with justice, and establish the evidence (as) before Allah.” (At-Talaq: 2)
This verse is mentioned after talking about divorce and raj`ah (taking the divorced wife back). The Shi`ah (Shiites) understand the order: “take for witness two persons” as that of command, while most of scho
lars understand it as that of recommendation.”
So, it is preferable to have witness for divorce and raj`ah, but this is not a condition.
This is also backed up by the fatwa issued by Sheikh Yusuf Al-Qaradawi in this context. He gave support to the view adopted by the majority of scholars that having witness for divorce or for raj`ah is not obligatory, but it’s mostly preferred for the latter, on the ground of the mentioned verse, which aims at preventing some kind of argument or confusion.