Showing Error “argument is not defined” while adding multiple arguments in arrow function but It’s Working in Normal Function call

//Example – 1

function add1(){

    if (arguments.length == 0){

        document.write("NO Argument Passed!");
    }
    else{

        let sum = 0;

        for(let num in arguments){

            sum += arguments[num];
        }

        document.write(sum);
    }
}

add1(5,10); 

In this example, I am getting the correct result.

//Example – 2 ( With Arrow Function)

let sum = () => {

    if( arguments.length == 0){

        document.write("NO Argument Passed!");
    }
    else{

        let sum1 = 0;

        for(let number in arguments){

            sum1 += arguments[number];
        }

        document.write(sum1);
    }


};

sum(10,20);

*Here I am getting an error in console “arguments is not defined”. Please tell me where I did Wrong.Thank you..!