John Gill Commentary Mark 13:6

"Many shall come in my name, saying, I am [he]; and shall lead many astray." — Mark 13:6 (ASV)

For many shall come in my name
Taking upon them the name of the Messiah: saying,

I am [Christ] ;
the word "Christ", is rightly supplied from (Matthew 24:5) ; otherwise in the original it is only, "I am"; which the Persic version doubles, reading it, "I am indeed, I am": he that was promised and expected, the true Messiah; he that was to come:

and shall deceive many; (See Gill on Matthew 24:5).