Church Fathers on Mark 16:20

The Lord Jesus, who had descended from heaven to give liberty to our weak nature, Himself also ascended above the heavens; wherefore it is said, 'So then after the Lord had spoken unto them, He was received up into heaven.'

By which words He seems to shew clearly enough that the foregoing discourse was the last that He spake to them upon earth, though it does not appear to bind us down altogether to this opinion. For He does not say, After He had thus spoken unto them, wherefore it admits of being understood not as if that was the last discourse, but that the words which are here used, 'After the Lord had spoken unto them, He was received into heaven,' might belong to all His other discourses.…

Observe that in proportion as Mark began his history later, so he makes it reach in writing to more distant times, for he began from the commencement of the preaching of the Gospel by John, and he reaches in his narrative those times in which the Apostles sowed the same word of the Gospel throughout the world.