[If] he declared to him, “My father is acceptable to me,” [or] “Your father is acceptable to me,” [or] “Three cattle herders are acceptable to me” —- R’ Meir says: He can retract. But the Sages say: He cannot retract. [If] he was under an obligation of oath to another, and he said, “Vow to me by the life of your head,” R’ Meir says: He can retract. The Sages, however, say: He cannot retract.