Leviticus 5:4
3 or when he touches human uncleanness with regard to anything by which he can become unclean, even if he did not realize it, but he has later come to know it and is guilty; 4 or when a person swears an oath, speaking thoughtlessly with his lips, whether to do evil or to do good, with regard to anything which the individual might speak thoughtlessly in an oath, even if he did not realize it, but he has later come to know it and is guilty with regard to one of these oaths—
Onkelos Leviticus 5:4
3 Or if he shall touch the uncleanness of a man, any uncleanness which defileth him, and it be hidden from him; but (afterwards) becometh aware of it and is guilty;— 4 or if a man makes an affirmation, declaring with his lips, for evil or for good, according to whatever the man shall declare by affirmation, and the truth is hidden from him, and he afterwards have knowledge thereof, he is guilty of one of these.
Notes and References
"... The targumist generally weakens scripture's 'swear' to an 'affirmation' because of the traditional Jewish reluctance to swear. However, he is inconsistent. For example, 'swear' is used in verses 22 and 24. He changes the conjugation of the first tishava (in the second person) to yishava (in the third person) to conform to the grammatical usage of the other verbs in the passage ..."
Drazin, Israel, and Stanley M. Wagner Onkelos on the Torah, Leviticus: Understanding the Bible Text (p. 28) Gefen, 2006