Oracle 18c

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create table table1(colnames varchar(10));
begin
	insert into table1(colnames) values('col1');
	insert into table1(colnames) values('col2');
	insert into table1(colnames) values('col3');
	insert into table1(colnames) values('col4');
end;
/
1 rows affected

create table table2(col1 int, col2 int, col3 int, col4 int);
begin
    insert into table2 values(1, 2, 3, 4);
    insert into table2 values(5, 6, 7, 8);
end;
/
1 rows affected

declare
	p_sql varchar2(100);
begin
	select 
	    'select ' 
	    || listagg('a1.' || colnames, ', ') within group(order by colnames)
	    || ' from table2 a1'
	into p_sql
	from table1;
	dbms_output.put_line('sql: ' || p_sql);
	execute immediate p_sql;
end;
/
1 rows affected

dbms_output:
sql: select a1.col1, a1.col2, a1.col3, a1.col4 from table2 a1