Please give clear explanation with steps(proper proof)

Consider the operation rest defined on languages with the alphabet by: rest(L)={ssLforany} Essentially, rest removes the first character from every string in the language that isn't empty. For example, rest ({,01,1001,00111})={1,001,0111} and rest ({0,1,00,10})= {,0} Prove that the class of regular languages is closed under rest