Riyad as-Salihin 1706
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] .
عن أم سلمة رضي الله عنها قالت قال رسول الله صلى الله عليه وسلم ‏:‏ ‏
"‏من كان له ذبح يذبحه، فإذا أهل هلال ذي الحجة، فلا  يأخذن من شعره ولا من أظفاره شيئًا حتى يضحي‏"‏ ‏(‏‏(‏رواه مسلم‏)‏‏)‏‏.‏