It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) forbade selling shares before their division.
Hadith Referenceسنن دارمي / من كتاب السير / 2512
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):إسناده صحيح نعم مكحول رأى أبا أمامة ولم يسمع منه ولكنه متابع عليه كما ترى، [مكتبه الشامله نمبر: 2519]
Hadith Takhrijاس حدیث کی سند صحیح ہے۔ دیکھئے: [طبراني 7594، 7774] ، [ابن منصور 7759] ، [مجمع الزوائد 6569]
Brief Explanation
(Commentary on Hadith 2511)
The prohibition of selling before the shares are divided is most likely because the sale is unknown (majhool); neither the quantity is known, nor the type and goods are known. Then how can buying and selling be valid?