Both Question and answer don't have sufficient information about target.

What is the purpose of IDENTITY_INSERT ?

And answer

SET IDENTITY_INSERT allows explicit values to be inserted into the identity column of a table.

SET IDENTITY_INSERT is not meaningful and you can not identify result until ON or OFF is not include in this statement. SET IDENTITY_INSERT it self not allows explicit values to be inserted into the identity column of a table until you don't include ON in this.