Riyad-us-Saliheen 484
'Abdullah bin Mughaffal (May Allah be pleased with him) reported: A man came to the Prophet (PBUH) and said, "O Messenger of Allah! By Allah, I love you." He (PBUH) said, "Think about what you are saying." The man repeated thrice, "I swear by Allah that I love you." He (Prophet (PBUH)) said, "If you love me, you should be ready for acute poverty; because poverty comes to those who love me, faster than a flood flowing towards its destination."
[At-Tirmidhi]