Umm Salamah (May Allah be pleased with her) said:
The Messenger of Allah (ﷺ) said, "When anyone of you intends to sacrifice the animal and enter in the month of Dhul-Hijjah, he should not get his hair cut or nails pared till he has offered his sacrifice."[Muslim].
App reference: Book 18, Hadith 196
Arabic/English book reference: Book 18, Hadith 1706