Sunan an-Nasa'i, Hadith 5722 ⓘ
It was narrated that Ya'la bin 'Ata' said: "I heard Sa'eed bin Al-Musayyab say, when a Bedouin asked him about a drink that had been cooked and reduced by half: 'No, not until two-third has gone and one-third is left.'"
أَخْبَرَنَا سُوَيْدٌ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ سُفْيَانَ، عَنْ يَعْلَى بْنِ عَطَاءٍ، قَالَ سَمِعْتُ سَعِيدَ بْنَ الْمُسَيَّبِ، وَسَأَلَهُ، أَعْرَابِيٌّ عَنْ شَرَابٍ، يُطْبَخُ عَلَى النِّصْفِ فَقَالَ لاَ حَتَّى يَذْهَبَ ثُلُثَاهُ وَيَبْقَى الثُّلُثُ .
also referenced under: Book 51, Hadith 184 (In-Book) & Volume 6, Book 51, Hadith 5725 (DarusSalam)