It is not mentioned how much time has passed since the events of the last episode of season 19, when Matt's arm was so badly wounded that it was expected to take months for him to fully recover - if he ever did. However, he is using it with no problems, including when he arm wrestles with Esau.
Matt is arm wrestling with Esau against a knife. There is no blood on either side, after Matt wins.
While Matt is on a chase with Laban, his rifle alternates between his hand and gun holster on the horse.
When the Wakefields are chasing Matt, the father says that they all have a share in his hide. Esau says, "It's gotta be me," but his lips say something completely different.
When one of the sons aims his rifle at Abraham, Abraham says, "Don't you raise you hand against me," but his lips say "sword," not "hand."
After Abraham comes out of his trance and finds out Isaac and Abel have gone after the marshal, he says, "I'll beat 'em to death," but is lips say one more word after "death."