How to return salaams to one who offers his hand in greeting during the khutbah

If the imaam is preaching and someone greets you and offers his hand,
what is the ruling?
Praise be to Allaah.
Gesture to him if it is the time of the khutbah, and put your hand in
his, without speaking, because the Messenger of Allaah (peace and
blessings of Allaah be upon him) commanded usto listen to the khutbah.
He said, "If you say to your companion on Friday, 'Listen!' when the
imaam is preaching, then you have engaged in idle speech." (Narrated
by al-Bukhaari, al-Jumu'ah, 882; Muslim, al-Jumu'ah, 1404. Agreed
upon).
He described his enjoiningsomething good as being "idle speech"
(laghw) at the time of the khutbah, so how about other kinds of
speech? And the Prophet (peace and blessings of Allaah be upon him)
said, according to a saheeh hadeeth, "Whoever plays with the pebbles
(on the ground) has engaged in idle speech (laghw)." (Narrated by
Muslim, al-Jumu'ah, 1419)
At Jumu'ah prayers, the believer should listen to the khutbah and be
humble and solemn, he should beware of playing with pebbles on the
ground or anything else. If someone greets him he should gesture to
him without speaking. If he puts his hand in his when he offers his
hand, without speaking, that is OK, as stated above. He should tell
him after the khutbah that he should not have done that, and that
which is prescribed if one comes in when the imaam is preaching is to
pray two rak'ahs to "greetthe mosque" and not to say salaams to anyone
until after the khutbah has ended. If he sneezes he should praise
Allaah (say "al-hamdu Lillah") to himself without speaking out loud.