Maliks Muwatta Book 18, Hadith Number 27.
Yahya related to me from Malik that he had heard that Umar ibn al-Khattab, if he was travelling in Ramadan and knew that he would reach Madina at the beginning of the day, would do so fasting.
Yahya said that Malik said, “Someone who is travelling and knows that he will be reaching his people in the first part of the day, and then dawn breaks before he gets there, should be fasting when he gets there.”
Malik said, “Someone who intends to go away (on a journey) in Ramadan, and then dawn breaks while he is still on his land before he has left, should fast that day.”
Malik said that a man who returns from a journey in Ramadan and is not fasting may have sexual intercourse with his wife if he wishes, if she is not fasting and she has just become pure after her menses.