Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said concerning the statement of Allah Almighty "So come to your tilth however you wish" [Surah al-Baqarah: 223]: "Tilth" means the private part; come from the front or from behind, in any manner, but do not go beyond the private part, as in the statement of Allah Almighty: "From where Allah has commanded you" [Surah al-Baqarah: 222].
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14110