John Gill Commentary Mark 5:42

"And straightway the damsel rose up, and walked; for she was twelve years old. And they were amazed straightway with a great amazement." — Mark 5:42 (ASV)

And straightway the damsel arose, and walked
As soon as ever the above words were pronounced by Christ, such divine power went along with them, that the child returned to life; and raised herself up from the bed, got off of it, and walked about the room in perfect health and strength:

for she was of the age of twelve years ;
and so, when alive and well, was able to walk; though one of this age was called a little one, as this is by another evangelist; (See Gill on Matthew 9:18),

and they were astonished with a great astonishment ;
they were exceedingly amazed at such a signal instance of the power of our Lord, even both the parents of the child, and the disciples of Christ.