Instruction Regarding Walima
Not long had passed that once, Hazrat Abdur Rahman (ra) bin Auf came before the Holy Prophet (sa) and had a mark of saffron on him. And so, the Holy Prophet (sa) asked if he had married and he replied in the affirmative. The Holy Prophet (sa) enquired who he got married to and he replied that it was with a woman belonging to the Ansar. The Holy Prophet (sa) then asked how much dowry he had given and he stated that he gave gold the size of a nugget, or he perhaps said a nugget of gold. Upon this, the Holy Prophet (sa) stated that he should hold a walima [a ceremony after the consummation of marriage], even if it be by offering a single sheep.
(Sahih al-Bukhari, Kitab-ul-Buyu‘, Bab Qaul Allah Wa Ahallallahu al-Bai‘a…’, Hadith 2048-2049)