It is narrated from the Prophet of Islam (PBUH) who said:

Prophet Shuaib (AS) cried so much for the love of Allah (SWT) until he became blind. Then, God granted his sight back to him, and this situation happened four times. On the fourth time, it was revealed to him: “O’ Shuaib, How long do you want to carry on like this? If you fear the hellfire, God has saved you from that, and if it is due to having desire for paradise, God has granted that to you.” Shuaib (AS) replied: O’ God, You are aware that I do not cry for fear of hell fire nor for my desire for paradise; rather my heart is attached to God’s love, I cannot see You and cannot wait. It was revealed to Shuaib (AS): Now that you feel like this, I will send you My Kalim, Mosa ibn Imran to serve you [1].

[1] Akhlaq, Allamah Shobbar, PP 409-10.

Source: en.shafaqna.com