Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: Whoever swears an oath and then says in sha' Allah has made the exception.
Imam al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators are the narrators of the Sahih, except that the narrator named al-Qasim did not live in the time of Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him).