Muwatta Imam Malik Book of Hajj, Hadith 195

Yahya related to me from Malik from Nafi that if Abdullah ibn Umar had finished the fast of Ramadan and intended to do hajj, he would not cut his hair or beard at all until he had done hajj.
Malik said, "It is not necessary for people to do the same."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ إِذَا أَفْطَرَ مِنْ رَمَضَانَ وَهُوَ يُرِيدُ الْحَجَّ لَمْ يَأْخُذْ مِنْ رَأْسِهِ وَلاَ مِنْ لِحْيَتِهِ شَيْئًا حَتَّى يَحُجَّ . قَالَ مَالِكٌ لَيْسَ ذَلِكَ عَلَى النَّاسِ .