Marriage vows are promises each partner in a couple makes to the other during a wedding ceremony based upon Western Christian norms. They are not universal to marriage and not necessary in most legal jurisdictions. They are not even universal within Christian marriage, as Eastern Christians do not have marriage vows in their traditional wedding ceremonies.
In the time of the Roman Empire (17 BC – 476 AD) the lower classes had "free" marriages. The bride's father would deliver her to the groom, and the two agreed that they were wed, and would keep the vow of marriage by mutual consent. Wealthy Romans, though, would sign documents listing property rights to publicly declare that their union was legalized and not a common law marriage. This was the beginning of the official recording of marriage.
The oldest traditional wedding vows can be traced back to the manuals of the medieval church. In England, there were manuals of the dioceses of Salisbury (Sarum) and York. The compilers of the first Book of Common Prayer, published in 1549, based its marriage service mainly on the Sarum manual. Upon agreement to marry, the Church of England usually offered couples a choice. The couple could promise each other to "love and cherish" or, alternatively, the groom promises to "love, cherish, and worship", and the bride to "love, cherish, and obey".
Couples wedding in the Roman Catholic Church essentially make the same pledge to one another. According to the Rite of Marriage (#25) the customary text in English is:
I, ____, take you, ____, to be my (husband/wife). I promise to be true to you in good times and in bad, in sickness and in health. I will love you and honour you all the days of my life.
In the United States, Catholic wedding vows may also take the following form:
I, ____, take you, ____, to be my lawfully wedded (husband/wife), to have and to hold, from this day forward, for better, for worse, for richer, for poorer, in sickness and in health, until death do us part.