أَخْبَرَنَا أَحْمَدُ بْنُ خَالِدٍ، عَنْ مَعْنٍ، قَالَ حَدَّثَنَا مُعَاوِيَةُ بْنُ صَالِحٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، قَالَ إِذَا طُبِخَ الطِّلاَءُ عَلَى الثُّلُثِ فَلاَ بَأْسَ بِهِ ‏.‏

It was narrated that Sa'eed bin Al-Musayyab said: "When At-Tila' (thickened grape juice) has been cooked and reduced to one-third, then there is nothing wrong with it." Translation Not Available

Book Ref: Sunan An Nisai Book 51 Hadith 5723
Web Ref:  Sunan An Nisai Vol 6 Book 51 Hadith 5726