John Gill Commentary Mark 4:11

"And he said unto them, Unto you is given the mystery of the kingdom of God: but unto them that are without, all things are done in parables:" — Mark 4:11 (ASV)

And he said unto them
His disciples;

unto you it is given to know the mystery of the kingdom of God ;
or the mysteries of the kingdom of heaven, the secrets of the Gospel dispensation, the mysterious doctrines of grace; (See Gill on Matthew 13:11),

but unto them that are without ;
"to strangers", as the Syriac and Arabic versions render it, who were not the disciples of Christ, nor admitted to any intimacy with him; who came only to amuse themselves with the sight of his person and miracles:

all [these] things are done in parables ;
are wrapped up in dark sayings, and figurative expressions, the sound of which they heard, and might be pleased with the pretty similes made use of, but understood not the spiritual meaning of them.