John Gill Commentary Mark 16:19

"So then the Lord Jesus, after he had spoken unto them, was received up into heaven, and sat down at the right hand of God." — Mark 16:19 (ASV)

So then, after the Lord
The Vulgate Latin and Syriac versions add, "Jesus"; and the Ethiopic version reads, "our Lord, the Lord Jesus"; and both Syriac and Persic read, "our Lord"; which is common in these versions, where the word "Lord" is used:

had spoken unto them ;
the disciples, the above words, which commissioned them where to go, what to do, and what to say; and what should follow them, for the confirmation of their mission and doctrine:

he was received up into heaven ;
in a cloud, angels attending him, and devils led captive by him, and with a welcome into his Father's presence:

and sat on the right hand of God ;
the Ethiopic version adds, "his own Father", and which is an evidence of his having done his work, and that to full satisfaction; and is an honour never conferred on angels, or any mere creature; and is a peculiar dignity conferred on the human nature of Christ, in union with his divine person; and here he will remain, till his second coming.