Dought & clear, - Words and deeds of the Prophet (peace and blessings of Allaah be upon him) before his mission began.

Are the deeds and words of the Messenger (peace and blessings of
Allaah be upon him) before his mission began regarded as Sunnah, such
as his marriage to Khadeejah (may Allaah be pleased with her)?.
Praise be to Allaah.
The basic principle is that the actions of the Prophet(peace and
blessings of Allaah be upon him) before his mission began are outside
of the legislative Sunnah, and that we are not required to follow him
or take him as an example in that regard, except in cases where
sharee'ah – after his mission began – affirmed that something was
prescribed or Islamically acceptable, either by way of being
obligatory or mustahabb, such as fulfilling promises, helping the
destitute, honouring guests, helping people when calamity strikes and
so on. In that case we are obliged to follow his example, because it
became a law for us after his Prophethood began, and not just because
he(peace and blessings of Allaah be upon him) did it before he was a
Prophet. Based on this, there are some actions that he did before his
mission began that we are not obliged to follow, either because there
is no proof that it is prescribed for us or because there are reports
to show that it was abrogated after his mission began.
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) said: The
things that happened before Prophethood are not mentioned as things to
be followed or that are legislated, as is the case with his actions
after Prophethood, because the Muslims are unanimously agreed that
what is obligatory with regard to believing in him(peace and blessings
of Allaah be upon him) and following what he brought, is that which
has to do with what happened after he became the Prophet.
Hence whoever stays away from Jumu'ah prayer and prayers in
congregation, and lives alone in caves and mountains, where there is
no Jumu'ah or prayer in congregation, and claims to be following the
example of the Prophet(peace and blessings of Allaah be upon him)
because he was used to worship alone in the cave of Hira' before his
Prophethood, thus forsaking the acts of worship that were prescribed
and enjoined by Allaah and His Messenger, and following the example of
what he used to do before Prophethood, is wrong. That is because,
after Allaah honoured him with Prophethood, the Prophet(peace and
blessings of Allaah be upon him) no longer did what he used to do
before that, of worshipping alone in the cave of Hira and so on.
None of his Sahaabah after him went to the Cave of Hira', and they did
not stay away from Jumu'ah prayer or prayers in congregation in
isolated places, and none of them observed any kind of forty-day
retreat, as some of the later Muslims did. Rather they worshipped
Allaah by means of the prescribed acts of worship that the
Prophet(peace and blessings of Allaah be upon him) ordained for them.
End quote fromMajmoo' al-Fataawa(18/10).
With regard to the muhaddithoon (scholars of hadeeth), they paid
attention to what was narrated from the Prophet(peace and blessings of
Allaah be upon him) at all times, even if it was before his mission
began. That is part of the Sunnah according to the definition of the
muhaddithoon, who regard everything that was narrated from the
Prophet(peace and blessings of Allaah be upon him) as Sunnah, so they
narrated it in their books on that basis.
See:Af'aal al-Rasool sall-Allaahu 'alayhi wa sallam wa Dalaalatuhaa
'ala al-Ahkaam, by Dr. Muhammad al-'Aroosi (149).
And Allaah knows best.And Allaah knows best.