Charles Spurgeon Commentary Mark 1:34

"And he healed many that were sick with divers diseases, and cast out many demons; and he suffered not the demons to speak, because they knew him." — Mark 1:34 (ASV)

And he healed many that were sick of various diseases, and cast out many devils; and suffered not the devils to speak, because they knew him.

They would persist in acknowledging him, perhaps with the design of injuring his cause. For nothing hurts the cause of Christ more than to have it praised by bad men or evil spirits.

I do not know that an outrageous sinner, if he will not repent, can do Christ a better service than to abuse him, for then he is speaking in his own natural way. But when the devil or his servants go into the pulpit and begin to speak in praise of Christ, then Christ's cause is in a bad situation indeed.

So he suffered not the devils to speak, because they knew him; or, as the margin puts it, even to say that they knew him.