Hawzah News Agency – It is narrated in Tuhaf al-Uqul:

قالَ اللَّهُ تعالى‏ لعيسى‏ عليه السلام: أدِّبْ قلبَكَ بالخَشْيةِ.

Allah, most High, told Jesus (AS), 'Refine your heart with piety'.

Source: Tuhaf al-Uqul, no. 500