It was narrated from Miqdad bin Aswad that:
He asked the Prophet about a man who approached his wife, but did not ejaculate. He said: "If anyone of you finds that, he should sprinkle water over his private part (meaning he must wash it) and perform ablution." (RU)
English reference (RU): Vol. 1, Book 1, Hadith 505 (RU)
Arabic reference (RU): Book 1, Hadith 544 (RU)