Yes permissible!
Sahih Bukhari 4171.
Narrated by Ibrahim (Rh) Nafi (R), he said, when Ibnu Umar (R) used to recite the Quran, he would not have spoken without recitation of the Quran recitation. Once I was able to read Surah Al-Baqar and found him. He reached at one place to read. Then he said, "You know, on what occasion has this verse revealed?" I said, no. Then he said, the verse was revealed about such and such and such. Then again he was reciting. Narrated Abdus Samad: He said, "My father narrated the hadith to me, he said, Ayub narrating to me the hadith, from Nafi and from Nafi bin Umar (R). So you can go as you wish in your fields. (2: 223). Rabi said, women can have sexual intercourse with the back. Muhammad bin Yahya bin Saeed from his father, from Ubaidullah, he narrated from Nafi and he narrated from Ibn Umar (ra).
Sahih Bukhari 4172.
Narrated by Abu Nuim (Jahir), he said that the Jews would say that if a person has sexual intercourse with a woman, then the child is tears. Then the revelations (rejection of their opinion) are revealed.