[One who says:] “I am a nazir, and [I am] a nazir when a son will be [born] to me” —- [if] he began to count his own, and then a son was born to him, he completes his own and then counts [that] of his son, [If he says:] “I am a nazir when a son will be [born] to me, and [I am] a nazir” —- [if] he began to count his own, and then a son was born to him, he sets aside his own and counts that of his son, and then completes his own.