Is Wine Vinegar Halal?
Question

Is wine and spirit vinegar halal, considering all vinegar is made from oxidising a form of alcohol and that normal vinegar is supposed to be halal?
Praise be to Allah.What is vinegar?
Vinegar is a well-known basic foodstuff, made from wine of which the composition has changed so that it is no longer sweet but is acidic or sour.
Jabir (may Allah be pleased with him) reported that the Prophet (peace and blessings of Allah be upon him) said: “What a good food vinegar is.” (Reported by Muslim, 3/1623)
Ruling on wine made from vinegar
When wine turns to vinegar by itself, without any deliberate treatment needed for it to be changed, it is permissible to eat, drink and handle, according to the consensus of the scholars, because of the hadith quoted above.
But if the wine has become vinegar because of deliberate treatment, by adding vinegar, onions, salt etc., or by any other process, in this case the scholars (may Allah have mercy on them) differ as to whether it is permissible.
The Shafi’is, Hanbalis and some of the Malikis say that it is not permissible to deliberately change wine to vinegar because then it is not pure. The evidence for this is the hadith of Anas ibn Malik (may Allah be pleased with him) who said: “The Messenger of Allah (peace and blessings of Allah be upon him) was asked whether wine could be changed to be used as vinegar. He said, ‘No.’” (Reported by Muslim).
Abu Talhah (may Allah be pleased with him) reported that the Prophet (peace and blessings of Allah be upon him) was asked about some orphans who had inherited some wine. He said, “Pour it away.” He was asked, “Could they not make it into vinegar?” He said, “No.” (Reported by Muslim).
Why is it not permissible to change wine to vinegar
The reason for this is:
Allah, may He be glorified and exalted, has commanded us to avoid wine. Keeping it and treating it until it turns into vinegar means handling it and being involved with it by storing it and benefiting from it, and this is not permitted.
It is permitted for a Muslim to buy vinegar from someone who is selling it, unless he realizes or comes to know that it was produced by means of a deliberate process. ‘Umar (may Allah be pleased with him) said: “… There is nothing wrong with a man buying vinegar from the people of the Book, if they sell it, so long as he knows that they did not deliberately process it from wine.” (Al-Mughni, 8/330)
And Allah knows best.
References
Bidayat al-Mujtahid li Ibn Rushd, 1/461.
Kashshaf al-Qina’ li’l-Bahuti, 1/187
Fath al-Qadir li Ibn al-Hammam, 8/166
Al-Majmu’ li’l-Nawawi, 1/225
Al-Mughni li Ibn Qudamah, 8/319.