Not in itself. If your arm impedes the ballhandler, it may be holding. If you hit them with your arm, that is also a foul. But "reaching in" is not the name of a foul.
This is covered on a list of 7 Basketball rule myths on NBA.com. (http://www.nba.com/jrnba/officials/officials_guide_section15.html)
1 rule is you can not run with the ball
There is no 90 second rule in basketball.
FIBA
because that is the rule...
basketball
Because that is the rule.
There are many like the shotclock violation, 8second rule
Dunking is not allowed.
no
Texas A&M
The shot clock.
One rule of basketballis that you can't run with the ball in your handds without dribbling.