SQL OPENQUERY, Incorrect syntax near ‘+’

I have this sql query:

DECLARE  @VAR varchar(8)
SET  @VAR = '20140202'
SELECT * FROM OPENQUERY([NMD],'SELECT * FROM NmdItemGroups01.dbo.InvTranDtl WHERE TranDate = ''' + @VAR + '''')

But when I run it, it gives this error:

Incorrect syntax near '+'

Answer

sp_executesql example:

DECLARE  @VAR varchar(8)
SET  @VAR = '20140202'

EXEC sp_executesql 
    N'SELECT * FROM NmdItemGroups01.dbo.InvTranDtl WHERE TranDate = @TranDate', 
    N'@TranDate DATE', 
    @VAR