Riyad as-Salihin

'Abdullah bin Mughaffal (May Allah be pleased with him) reported: A man came to the Prophet (ﷺ) and said, "O Messenger of Allah! By Allah, I love you." He (ﷺ) said, "Think about what you are saying." The man repeated thrice, "I swear by Allah that I love you." He (Prophet (ﷺ)) 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, who classified it as Hadith Hasan].