Question Summary:
What is the Du’aa to be read when consummating the marriage?

Question Detail:

Is the husband supposed to read a dua keeping his hand on his wife's forehead after nikah? Is this a valid hadeeth? 

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
You enquire regarding the following Hadith:
عَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، عَنِ النَّبِيِّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ قَالَ: «إِذَا تَزَوَّجَ أَحَدُكُمُ امْرَأَةً أَوِ اشْتَرَى خَادِمًا، فَلْيَقُلِ اللَّهُمَّ إِنِّي أَسْأَلُكَ خَيْرَهَا وَخَيْرَ مَا جَبَلْتَهَا عَلَيْهِ، وَأَعُوذُ بِكَ مِنْ شَرِّهَا وَمِنْ شَرِّ مَا جَبَلْتَهَا عَلَيْهِ، وَإِذَا اشْتَرَى بَعِيرًا فَلْيَأْخُذْ بِذِرْوَةِ سَنَامِهِ وَلْيَقُلْ مِثْلَ ذَلِكَ». قَالَ أَبُو دَاوُدَ: زَادَ أَبُو سَعِيدٍ، ثُمَّ لِيَأْخُذْ بِنَاصِيَتِهَا وَلْيَدْعُ بِالْبَرَكَةِ فِي الْمَرْأَةِ وَالْخَادِمِ
Translation: Hadhrat Abdullah ibn Amr ibn al-'As narrates that Rasulullah (ﷺ) said: “If one of you marries a woman or buys a slave, he should say:
اللَّهُمَّ إِنِّي أَسْأَلُكَ خَيْرَهَا وَخَيْرَ مَا جَبَلْتَهَا عَلَيْهِ، وَأَعُوذُ بِكَ مِنْ شَرِّهَا وَمِنْ شَرِّ مَا جَبَلْتَهَا عَلَيْه
"O Allah, I ask You for the good in her, and in the good disposition You have given her; I take refuge in You from the evil in her, and in the evil disposition You have given her." When he buys a camel, he should take hold of the top of its hump and say the same kind of thing.
Abu Dawud (Rahimahullah) said: Abu Sa'id added the following words in his version: He should then take hold of her forelock and pray for blessing in the case of a woman or a slave.[1]
This Hadith is authentic. Thus, after the Nikah, the newly-wed groom/husband should place his hand on the forehead of his newly-wed bride and recite the above-mentioned Duaa.  
And Allah Ta’āla Knows Best
Abdullah ibn Mohammed Aijaz
Student Darul Iftaa
Baltimore, USA
Checked and Approved by,
Mufti Ebrahim Desai.