Tawoos says that in the beginning, the opinion of Sayyiduna Ibn Umar (may Allah be pleased with them both) was that a woman cannot go for jihad, but later I heard him say that the Prophet (peace and blessings of Allah be upon him) had also permitted women.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5765