Riyad as-Salihin 34
Anas (May Allah be pleased with him) said:
I heard the Messenger of Allah (ﷺ) saying, "Allah, the Glorious and Exalted said: 'When I afflict my slave in his two dear things (i.e., his eyes), and he endures patiently, I shall compensate him for them with Jannah.". [Al-Bukhari] .
وعن أنس رضي الله عنه قال‏:‏ سمعت رسول الله صلى الله عليه وسلم يقول ‏:‏ ‏
"‏إن لله عزوجل قال‏:‏ إذا ابتليت عبدي بحبيبتيه فصبر عوضته منهما الجنة‏"‏ 

(‏‏(‏رواه البخاري‏)‏‏)‏‏.‏