A.T. Robertson Commentary Mark 8:34

"And he called unto him the multitude with his disciples, and said unto them, If any man would come after me, let him deny himself, and take up his cross, and follow me." — Mark 8:34 (ASV)

And he called unto him the multitude with his disciples (κα προσκαλεσαμενος τον οχλον συν τοις μαθηταις αυτου). Mark alone notes the unexpected presence of a crowd up here near Caesarea Philippi in heathen territory. In the presence of this crowd Jesus explains his philosophy of life and death which is in direct contrast with that offered by Peter and evidently shared by the disciples and the people. So Jesus gives this profound view of life and death to them all.

Deny himself (απαρνησασθω εαυτον). Say no to himself, a difficult thing to do. Note reflexive along with the middle voice. Ingressive first aorist imperative. See on Mt 16:24 about taking up the Cross. The shadow of Christ's Cross was already on him and one faces everyone.