Why does Ross say the following in Act IV, Scene 3 of Macbeth?
When Macduff asks Ross about his family, Ross replies, "...they were well at peace when I did leave 'em." Explain why he gives this answer and what it might mean.
In Shakespeare's Macbeth, Ross is hesitant to share such bad news with Macduff. He simply doesn't want to break the bad news to him.
Notice that it just takes a little prodding before he gives up the information. He is not trying to lie or keep anything from Macduff, he is just reluctant.
He may be a little intimidated, too. Macduff is a fierce warrior, and Ross's news is not good.
When this is performed, actors who play Ross often show this in their facial expressions and verbal hesitations, as if Ross is sizing up the situation and just gives up saying what he should say at the last second.
This is one of the moments that is left to directors and actors to interpret and perform accordingly. But one thing is certain, Ross means no harm.
Please note that this is in Act IV, Scene 3. I have changed your question, but you originally said Act 5 and I just want to make sure you know...
I believe that Ross is simply reluctant to tell Macbeth the truth about what has happened. I suppose it is possible that he left Scotland while Macduff's family was still alive and only heard about the murders on his way. But that does not really change what I am saying.
Ross has the horrible job of having to tell someone that his wife and kids have been murdered. It was pretty dumb of him, in my opinion, to try to avoid saying it, but you can certainly see why he would want to avoid it. That is why he says the lines you mention, in my opinion.