Ibn Kathīr wrote in Al-Bidāyah wa An-Nihāyah (11/213):

«كان شديداً على أهل البدع والمعاصي، وكان كبير القدر تعظمه الخاصة والعامة» "He was severe against the people of innovation and sin. He was highly esteemed, respected by both the elite and the common folk." Ibn Rajab also said in Ṭabaqāt Al-Ḥanābilah: «شيخ الطائفة في وقته ومتقدمها في الإنكار على أهل البدع والمباينة لهم باليد أو اللسان» "He was the leading figure of his time, at the forefront of denouncing the people of innovation and opposing them, whether by hand or by speech." Even Harshness Towards Ahlus-Sunnah Can Sometimes Be Necessary Imām Aḥmad ibn Ḥanbal (may Allāh have mercy on him), would sometimes criticise righteous individuals if they acted contrary to the Sunnah. However, his words were always rooted in sincere counsel for the sake of religion. [Manāqib Al-Imām Aḥmad by Ibn Al-Jawzi, p. 253] Unfortunately, we live in an era where many have abandoned this approach. Instead of confronting innovation with severity, they have adopted a softer approach—replacing firmness with leniency, complacency, and appeasement. What would have been more appropriate and beneficial is for them to stand united in opposing innovation and its proponents with severity and humiliation, just as the Salaf did. Had this approach been maintained, innovation and its adherents would have faded, the land would have been cleansed of their influence, and the light of the Sunnah would have illuminated its expanse.