A man said to the Prophet (peace be upon him): By Allah, O Messenger of Allah, I do love you. The Prophet (peace be upon him) said: Look, what you are saying? The man said: By Allah, I love you, and repeated this sentence thrice. The Prophet (peace be upon him) said: If you really love me, then be prepared for acute poverty, for extreme hardship rushes more rapidly towards a person who loves me, than a flood flows towards its goal. "

(Narrated Abdullah ibn Mughaffal - al-Tirmidhi) [src: alim.org]

Narrated by Ubayy ibn Ka'b (Radi Allah Ta'lah Anhu): "I said: Allah's Messenger (Sal-allahu-aleihi-wasallam), I invoke blessings upon you very frequently. How much of my supplication should I devote to you. He said: As much as you like. I said: May it be a quarter? He said: As much as you like, but if you increase it, it will be good for you. I said: May it be a half? He said: As much as you like, but if you increase it, it will be good for you. I said: May it be two thirds? He said: As much as you like but if you make an increase in it, it will be better. I said: May I devote the whole of my supplication to you (that I make in my prayer)? Thereupon he said: In that case it will take care of you and your sins would be expiated."

Tirmidhi transmitted it. Hadith No. 929 of Mishkat al-Masabih. [src: road-to-heaven.com]