undoubtedly safa and marwah* are among the symbols of allah so there is no sin on him for whoever performs the hajj of this house or the umrah to go back and forth between them and whoever does good of his own accord then indeed allah is most appreciative the all knowing. 
إن الصفا والمروة من شعائر الله فمن حج البيت أو اعتمر فلا جناح عليه أن يطوف بهما ومن تطوع خيرا فإن الله شاكر عليم