A woman was sometimes allowed to be impregnated by someone other than her husband, but the sons born of her would then become her husband's sons. Such sons were called ksetra jata. Because Rathitara had no sons, he took advantage of this method

Expressions researched:
"a woman was sometimes allowed to be impregnated by someone other than her husband, but the sons born of her would then become her husband's sons. Such sons were called kṣetra jāta. Because Rathītara had no sons, he took advantage of this method"

SB Canto 9

A person possessing an agricultural field may employ another person to produce food grains from it, but because the grains are produced from the land, they are considered the property of the owner of the land. Similarly, a woman was sometimes allowed to be impregnated by someone other than her husband, but the sons born of her would then become her husband's sons.

SB 9.6.2, Translation and Purport:

Rathītara had no sons, and therefore he requested the great sage Aṅgirā to beget sons for him. Because of this request, Aṅgirā begot sons in the womb of Rathītara's wife. All these sons were born with brahminical prowess.

In the Vedic age a man was sometimes called upon to beget sons in the womb of a lesser man's wife for the sake of better progeny. In such an instance, the woman is compared to an agricultural field. A person possessing an agricultural field may employ another person to produce food grains from it, but because the grains are produced from the land, they are considered the property of the owner of the land. Similarly, a woman was sometimes allowed to be impregnated by someone other than her husband, but the sons born of her would then become her husband's sons. Such sons were called kṣetra jāta. Because Rathītara had no sons, he took advantage of this method.