It is narrated from ‘Ikrimah (may Allah have mercy on him) regarding «﴿فَأْتُواحَرْثَكُمْأَنَّىشِئْتُمْ ...﴾»[البقرة: 223/2], that it means a man may have intercourse with his wife standing, sitting, from the front or from behind, from whichever direction he wishes.
Hadith Referenceسنن دارمي / من كتاب الطهارة / 1168