"The Messenger of Allah  (صلى الله عليه وآله وسلم) said:‘Verily Allah the Almighty has prescribed the obligatory deeds, so do not neglect them; He has set certain limits, so do not go beyond them; He has forbidden certain things, so do not indulge in them; and He has said nothing about certain things, as an act of mercy to you, not out of forgetfulness, so do not go enquiring into these.‘"

[It was narrated on the authority of Abi Tha'labah Al-Khushani Jurthum bin Nashir, radiyallahu 'anhu - Related by Al-Daraqutni and others - Al-Nawawi said this is a hasan (fine) hadith]

" إِنَّ اللهَ تَعَالَى فَرَضَ فَرَائِضَ فَلاَ تُضَيِّعُوهَا، وَحَدَّ حُدُوداً فَلاَ تَعْتَدُوهَا، وَحَرَّمَ أَشْيَاءَ فَلاَ تَنْتَهِكُوهَا، وَسَكَتَ عَنْ أَشْيَاءَ رَحْمَةً لَكُمْ غَيْرَ نِسْيَانٍ فَلاَ تَبْحَثُوا عَنْهَا"
[حَدِيثٌ حَسَنٌ رَوَاهُ الدَّارَقُطْنِي وَغَيْرُهُ]

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]