(a) It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that he disliked keeping oil in something made of elephant bone. In another place the words are: He disliked (using) elephant bones.
(b) Imam al-Bayhaqi (may Allah have mercy on him) said: It is transmitted from Ata, the Successor (may Allah have mercy on him), that he considered it disliked to benefit from the bones and tusks of elephants.
(c) It is transmitted from Tawus (may Allah have mercy on him) and Umar bin Abd al-Aziz (may Allah have mercy on him) that they both considered the use of ivory disliked.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 96