Marriage Fiqh: At least two witnesses are required for Marriage/Nikah

For an Islamic Nikah at least two witnesses are also required .Rasool salal laho aliehi wasalam said
“There is no Nikah without wali and two just witnesses”(Darqutnee)

The purpose of this condition is that married couple should not be accused of adultery and if some body accuses them the witnesses can make sure that it is wrong accusation.