Sahih Muslim
The Book of Virtue, Good Manners and Joining of the Ties of Relationship (Kitab Al-Birr was-Salat-I-wal-Adab)
Book Number: 032 / Hadith Number: 6378
Anas b. Malik reported that a desert Arab said to Allah's Messenger (may peace be upon him): When would be the Last Hour? Allah's Messenger (may peace be upon him) said: What preparation have you made for that? Thereupon he said: The love of Allah and of His Messenger (that is my preparation for the Last Hour) (for the Day of Resurrection). Thereupon he (the Holy Prophet) said: You would be along with one whom you love.