Dear brother Yahia,
Wa alaikum assalam
The verb
'infadda' simply means to
disperse, break-away, separate or to scatter, implying they would have left the presence of the Prophet. In the context of the verse, this does not automatically mean that they would have become disbelievers.
Please also kindly note how the same verb is used in verses
62:11 and
63:7 to imply the action of dispersing from a particular place / location.
It remains noteworthy that even the Prophets were expected and reminded to pass on the message / conduct their affairs in the best possible way
(even though the situation may be testing), so that the audience would remain inclined to listen / take heed. A similar sentiment of preaching in the best possible manner can also be noted in verse 20:44 as an instruction to Prophet Moses as to how to interact with the tyrant Pharaoh with gentle speech, implying no harshness, frustration or rudeness in any form.
[1]I hope this helps, God willing
Joseph
REFERENCE:[1] SPEAK A GENTLE WORDhttp://quransmessage.com/articles/speak%20a%20gentle%20word%20FM3.htm