“But Iesus answered, and said, Ye know not what ye aske. Are ye able to drinke of the cup that I shall drinke of, and to be baptized with the baptisme that I am baptized with? They say vnto him, We are able.”
1611 King James Version (KJV)
20:22 Ye know not what is implied in being advanced in my kingdom, and necessarily prerequired thereto. All who share in my kingdom must first share in my sufferings. Are you able and willing to do this? Both these expressions, The cup, the baptism, are to be understood of his sufferings and death. The like expressions are common among the Jews.
Mt 20:22 Ye know not what ye ask. An illustration, this of ignorant prayer. Within a month they saw the places on his right hand and left occupied by the two thieves in the crucifixion (Mt 27:38). Are ye able to drink of the cup? The "cup" is an Old Testament image of a man's lot, or portion, as holding what of life God pours out for him. See Ps 11:6 16:5 23:5 73:10 75:8 116:13 Eze 23:33. Be baptized with the baptism I am baptized with? Baptism is the necessary condition by which one can enjoy the privileges of the church. The "cup" signifies suffering voluntarily taken, or "drunk", and the baptism what is endured at the hands of others. We are able. They no doubt thought they were. They loved their Lord, as well as pre-eminence, and felt that they were willing to go with him through suffering. They, however, overestimated their strength.