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.
As far as we know, there is no Hadeeth reported from the Prophet, sallallaahu ‘alayhi wa sallam, saying that the newlywed couple should offer a two-rak‘ah prayer at the consummation of marriage. But there is only a Mawqoof tradition (i.e. narrated by a companion who did not ascribe it to the Prophet, sallallaahu ‘alayhi wa sallam) concerning it from Ibn Mas‘ood . It is narrated on the authority of Shaqeeq Ibn Salamah that he said: A man called Abu Jareer came to ‘Abdullaah (Ibn Mas’ood) and said: “I married a young girl, and I fear that she might dislike me.” ‘Abdullaah said: “Affinity is from Allaah, and aversion is from Satan, who likes to make hateful to you what Allaah has made lawful to you. So, when she comes to you (to consummate marriage with her), order her to offer a two-rak‘ah prayer behind you.” [At-Tabaraani in his Mu‘jam; and Ibn Abi Shaybah in his Musannaf]
However, it is favorable to act upon that tradition, in offering a two-rak‘ah prayer at the consummation of marriage, and it is preferable that the husband should lead his wife in prayer, and she should stand behind him in prayer according to the mentioned tradition.
However, some scholars of Fiqh such as the late Shaafi‘i scholars, counted this prayer among those in which congregation is not legislated; but the narrations related about this prayer clearly state that it should be offered in congregation. These narrations are authenticated by Al-Albaani in his book “Aadaab Az-Zifaaf-Etiquette of marriage and wedding”.
Allaah Knows best.