A man had sexual intercourse with his wife after performing Tawaaf Al-Ifaadhah and before throwing the pebbles.

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.

If the questioner is implying the pebbles that are to be thrown in the days of Tashreeq, which are the eleventh, twelfth and thirteenth of Thul Hijjah for whoever delays or just the eleventh and twelfth for whoever hastens, then having sexual intercourse before doing so is permissible and one who does so is not required to do anything.

However, if you mean throwing the pebbles of Al-‘Aqabah on the Day of An-Nahr (i.e. the day of ‘Eed), then if he did this after performing Tawaaf Al-Ifaadhah and Sa‘y, even  if he was performing a Tamattu‘, Qiraan or Ifraad Hajj and did not yet perform Sa‘y after Tawwaf Al-Qudoom, then his Hajj is not invalidated. This is the opinion held by the majority of scholars including the four Imaams. Nevertheless, they held different opinions as to what he is required to do.

What seems preponderant from the scholars' opinions is that it is obligatory upon such to slaughter a sheep as a Fidyah (i.e. compensation) and the meat of which should be distributed among the poor of Al-Haram (i.e. the sacred precincts of Makkah).

Allaah Knows best.