Kitab Al-Nawadir fil-Lugha.

Abi Zayd Sa’Id b. Aws b. Thābit al-Anṣārī (739–830) was a famous Arab lexicographer and grammarian of the Basran School, who belonged to the Medina tribe of the Banū l-Khazraj.
Al-Nawadir records words that are rarely used in any of the four sources of linguistic data, dialectical differences, anomalous forms, and expressions, as well as data on synonyms, homonyms, addad (words with two contradictory meanings), ibdal (substitution of consonants and semivowels), elusions of Hamza, etc.
The al-Nawadir is divided into fifteen chapters, two of which are on poetry, seven on rajz and six on nawadir. It gained a major reputation and was quoted in many sources. Azhari (d. 370/981), for example, in his introduction of Tahzib al-Luga specifically mentioned al- Nawadir among the sources he relied on in compiling his dictionary, and praised the work for its rare material.