(a) Abdullah bin Maslamah al-Qa'nabi narrates it from Malik (may Allah have mercy on him).
(b) It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that he (peace and blessings be upon him) ordered "trimming the moustaches and letting the beard grow," and the wording of al-Qa'nabi's hadith is that the Messenger of Allah (peace and blessings be upon him) ordered "trimming the moustache and letting the beard grow."
(b) It is as though the Imam took ihfa' to mean trimming the moustache thoroughly, not shaving it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 700