The majority of scholars consider the Tawaaf al-Quduum to be a Sunnah. The Maaliki consider the Tawaaf al-Quduum to be Waajib, in association with certain conditions, for the one performing the Hajj al-Qiraan and Hajj al-Ifraad.
According to the majority of scholars it is not permissible to perform the Sa'y prior to the Tawaaf. If someone performs Sa'y prior to Tawaaf then his Sa'y is not correct according to this view. Since Sa'y is a Rukn from the 'arkaan of Hajj, the person will have to redo the Sa'y if he wants his Hajj to be valid.
Ibn Uthaymiin is of the opinion that if someone performs the Sa'y prior to the Tawaaf then it suffices though one should not do so. His evidence is the following Hadith:
Usamah bin Sharik said “I went out with the Prophet (sallallaahu alayhi wa sallam) to perform Hajj, and the people were coming to him. One would say “Apostle of Allaah(sallallaahu alayhi wa sallam) I ran between Al Safa’ and Al Marwah before going round the Ka’bah or I did something before the its proper time or did something after its proper time. He would reply “No harm will come; no harm will come except to one who defames a Muslim wrongfully. That is the one who will be in trouble and will perish?
[Sunan Abi Dawud Hadith No. 2015]