ENOfficial
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.'"
Source: sunnah.com
Other translations
Arabic
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 .
sunnah.com