Narrated Ibn 'Umar (RA):
"Allah's Messenger (ﷺ) said: "Whoever swears an oath, and then says: "If Allah Wills", he is not held accountable if he breaks it."[Ahmad and al-Arba'a reported it, and Ibn Hibban graded it Sahih (authentic)]. (AR)
Reference (AR): Bulugh al-Maram 1378 (AR)
In-book reference (AR): Book 13, Hadith 5 (AR)
English translation (AR): Book 13, Hadith 1378 (AR)