What is the ruling on one who begins the tawaf at al-Marwah?

The questioner : He says: Honorable Shaykh, what is the ruling on one who began the sa'y at al-Marwah and ended at al-Safa? He had already shaved his head and put on his clothes, and he believed that al-Marwah was al-Safa.

The Shaykh : If he began with al-Marwah in the sa'y, then the first lap is invalid. He must perform seven laps in addition to the first lap that was invalidated. If he does not do so, his sa'y is deficient by one lap.
Then, does he complete this lap if he remembers, or if he becomes aware, whether he was ignorant or not, or must he repeat the sa'y from the beginning? This depends on the disagreement among scholars: is continuity in the sa'y a condition for its validity, or is continuity in the sa'y a recommended practice and not a condition? There are two opinions among the followers of Imam Ahmad (may Allah have mercy on him). Some hold that continuity in the sa'y is a recommended practice and not a condition. Based on that, we say to this questioner: go back now, put on the ihram garments, and complete the sa'y with one lap, then shave or shorten your hair.
And according to the second opinion, which states that continuity is a condition, we say: take off your clothes now, go, and begin the sa'y from the start, performing seven laps, then shave or shorten your hair. This second option is more cautious, because if a person does it and repeats the sa'y from the beginning, his obligation is discharged with certainty. Yes.