Is there any sahih ruling of performing nikah in the masjid.i know of a hadith in tirmizi which is weak..any proof of any sahaabahs nikah beig performed in the masjid.how and where did muhammad (s.a) perform his daughters nikah ?

Praise
be to Allah.

There
is no saheeh hadeeth to suggest that it is mustahabb (encouraged) to do the
marriage contract in the mosque; rather there is no evidence for believing
that it is mustahabb to do it in the mosque. Shaykh Ibn ‘Uthaymeen (may
Allah have mercy on him) said: 

I do
not know of any basis or evidence from the Prophet (blessings and peace of
Allah be upon him) to suggest that it is mustahabb to do the marriage
contract in the mosque. But if it so happens that the husband and the
guardian of the woman are present in the mosque and they do the marriage
contract, there is nothing wrong with that. But as for that being mustahabb
in the sense that we would tell them to leave the house and go to the
mosque, or make an appointment to meet in the mosque and do the marriage
contract there, this is something for which evidence is required, and I do
not know of any evidence to that effect.

End
quote. Liqa’ al-Baab al-Maftooh, 167/17 

Rather
some of the fuqaha’ regarded it as mustahabb to do the marriage contract in
the mosque for the sake of the barakah (blessing) of the place, and so that
the news of the marriage would become widely known, and some of them also
based this on the da‘eef hadeeth that speaks of that. 

See:
al-Mawsoo‘ah al-Fiqhiyyah, 37/214, 41/221 

See
also the answer to question no. 132420 

Similarly, many people nowadays think that it is mustahabb, because if the
marriage contract is done in the mosque, this will prevent many of the
actions that are contrary to Islamic teachings, but usually happen if the
marriage contract is done somewhere other than in the mosque, such as haraam
mixing of the sexes, smoking, listening to music and other things that are
prohibited. 

With
regard to the question of where the Prophet (blessings and peace of Allah be
upon him) did the marriage contract for his daughters, this is something for
which we do not know of any evidence in the reports. It does not seem that
the location of that was something that people at that time attached any
importance to, which would make them want to find out about it and transmit
it to us. Rather that happened – as would appear to be the case – in their
ordinary gatherings or in their houses or wherever they happened to be, and
we have not found any report that speaks specifically about that. 

And
Allah knows best.