John Gill Commentary Mark 13:5

"And Jesus began to say unto them, Take heed that no man lead you astray." — Mark 13:5 (ASV)

And Jesus answering them
His four disciples, Peter, John, James, and Andrew: "began to say"; or "said", a way of speaking frequent with this evangelist:

take heed lest any man deceive you; (See Gill on Matthew 24:4).