From the Qing-era novel 《
飞龙全传》 (Feilong Quanzhuan, by
吴璿 Wu Xuan): the full couplet runs
酒逢知己千杯少,
话不投机半句多 — 'with kindred spirits, a thousand cups are few; with the wrong company, half a sentence is too many.' The two halves are still often quoted together.