Imam Ahmad (rahimahullah):

I strongly advise you and myself with the Taqwa* of Allah, The Magnificent, and to adhere to the Sunnah, for indeed you have learnt what has befell those who opposed it and what has come to those who follow it.

Tabaqaat Al-Hanaabilah v.1 pg.342

*Definition of Taqwa by the Taabi’ee Talq ibn Habeeb (died 100H rahimahullah)

‘’It is to act in obedience to Allah, with a light from Allah (i.e. Eemaan) and hoping for Allaah’s Mercy. And that you abandon disobedience to Allah with a light from Allah and fearing the punishment of Allah. [Reported by Ibn Abee Shaybah 11/33 and Ibnul Mubaarak in Az-Zuhd 473]