Ruling on one who starts sa‘i with al-Marwah before as-Safa

What the one who does sa‘i between as-Safa and al-Marwah
must do is begin with that with which Allah, may He be exalted, began
and with which His Messenger (blessings and peace of Allah be upon him)
began. Allah, may He be exalted, says (interpretation of the meaning):
“Verily!
As-Safa and Al-Marwah (two mountains in Makkah) are of the Symbols of
Allah. So it is not a sin on him who perform Hajj or Umrah (pilgrimage)
of the House (the Ka‘bah at Makkah) to perform the going (Tawaf) between
them (As-Safa and Al-Marwah). And whoever does good voluntarily, then
verily, Allah is All-Recogniser, All-Knower”
[al-Baqarah 2:158].

The Prophet (blessings and peace of Allah be upon him) began
his sa‘i with as-Safa, and he said: “I begin with that with which Allah
began.” The more correct view is that doing sa‘i in the proper order is
obligatory. So the one who begins with al-Marwah first cannot count his
first lap, and he must do another lap. 

Shaykh Muhammad al-Ameen ash-Shinqeeti (may Allah have mercy
on him) said: 

It must be understood that the majority of scholars stipulate
that sa‘i must be done in the proper order, which means beginning at as-Safa
and ending at al-Marwah. If he starts at al-Marwah, that lap is not counted.
Among those who stipulated that it must be done in the proper order are:
Maalik, ash-Shaafa‘i and Ahmad, and their companions, and al-Hasan al-Basri,
al-Awzaa‘i, Dawood and the majority of the scholars. 

Conflicting views were narrated from Abu Haneefah concerning
that: 

The author of Tabyeen al-Haqaa’iq Sharh Kanz al-Daqaa’iq,
which is a book on the fiqh of Imam Abu Haneefah (may Allah have mercy
on him), said:

If a person begins sa‘i from al-Marwah, the first lap should
not be counted, because he has gone against the command. End quote. 

Shaykh Shihab ad-Deen Ahmad ash-Shalabi said, in his footnote
to Tabyeen ad-Daqaa’iq:

With regard to his words “If a person begins sa‘i from al-Marwah,
the first lap should not be counted”, in Manaasik al-Karmaani it
says: Doing it in a certain order is not an essential condition, according
to our view; even if he begins at al-Marwah and comes to as-Safa, that is
acceptable and he may count it, but it is makrooh because he did not do what
is Sunnah. Therefore it is recommended for him to repeat that lap. 

As-Sarooji (may Allah have mercy on him) said in al-Ghaayah:
There is no basis for what al-Karmaani said: 

Ar-Raazi (may Allah have mercy on him) said in Ahkaam
al-Qur’an: If he begins with al-Marwah before as-Safa, that is not to be
counted according to the well-known report from our companions. It was
narrated from Abu Haneefah that he should repeat that lap, but if he does
not do so there is no blame on him. He regarded it as being like failing to
follow the proper order of washing the limbs when purifying oneself. End
quote. With regard to as-Sarooji’s comment that there is no basis for what
al-Karmaani said, that is subject to further discussion. End quote from
ar-Raazi. 

The evidence quoted by the majority for it being essential to
do sa‘i in the proper order is the fact that the Prophet (blessings and
peace of Allah be upon him) did that and said: “I begin with that with which
Allah began.” According to a report narrated by an-Nasaa’i he said: “Begin
with that with which Allah began,” in the form of a command or instruction.
Moreover, he said: “Learn from me your rituals of Hajj.” So we must learn
from him and follow him with regard to our rituals, and begin with that with
which Allah began, and following that which he (blessings and peace of Allah
be upon him) did, acting in accordance with the Holy Qur’an. 

End quote from Adwa’ al-Bayaan (5/250, 251) 

The scholars of the Standing Committee said – in response to
a question about someone who began with al-Marwah instead of as-Safa, and
added an eighth lap: 

If the matter is as you describe, that you did an eighth lap
to complete the seven laps of sa‘i in the correct order, then your sa‘i is
valid, because the first lap that you did, beginning at al-Marwah and ending
at as-Safa, is regarded as invalid, as you did not do it in the prescribed
manner. 

Shaykh ‘Abd al-‘Azeez ibn ‘Abdullah ibn Baaz, Shaykh ‘Abd
ar-Razzaaq ‘Afeefi, Shaykh ‘Abdullah ibn Ghadyaan. 

End quote from Fataawa al-Lajnah ad-Daa’imah li’l-Buhooth
al-‘Ilmiyyah wa’l-Ifta’ (11/259, 260) 

And Allah knows best.