Marriage: the principal and original self-gift is the unitive, mutual self-gift of the spouses to each other. In their marriage promises, the spouses pledge love and fidelity for as long as they live. The transmission of life is a sublime, concrete realization of this radical self-gift between a man and a woman. The mutual married love of man and woman ―becomes an image of the absolute and unfailing love with which God loves man[kind],‖21because as mutual self-gift, it is at the same time creative self-gift. The unitive and the procreative meanings of marriage are joined because they are two aspects of the same self-giving."

-USCCB Pastoral Letter