King James Version Mt 26:38 "Then saith he unto them, My soul is exceeding sorrowful, even unto death: tarry ye here, and watch with me."
Old English is not easily understood by many, myself included.
To get the right flavor of this verse, it would be best to read a literal translation from this forum.Greens Literal Translation explains this verse very well.
To get a better understanding, it is usually best to read the verses prior to the verse in question.Reading the whole chapter would be even better.
Here is how Green's literal Translation reads: " Matthew 26:36-38,"Then Jesus came with them to a place called Gethsemane. And He said to the disciples, Sit here, until going away, I shall pray there. 37 And taking along Peter and the two sons of Zebedee, He began to grieve and to be deeply troubled. 38 Then He said to them, My soul is deeply grieved, even unto death. Stay here and watch with Me."
Jesus was deeply grieved, because they were coming to take him away to be questioned, tortured and put to death.So,he asked his three closest disciples to stay with him.
We should remember, the Bible was not originally written in 16th century English.For better understanding of the scriptures, modern English Bible makes more sense.