Adam Clarke on John 15:20

If they have kept my saying - Or, doctrine. Whosoever acknowledges me for the Christ will acknowledge you for my ministers.

Some translate the passage thus: If they have Watched my sayings, i.e. with an intent to accuse me for something which I have said, they will Watch yours also: therefore be on your guard. Παρατηρειν has this sense, as we have had occasion to observe before; and perhaps τηρειν has the same sense here, as it is much more agreeable to the context.