Musannaf Ibn Abi Shayba 16:843

Abu Bakr narrated to us, he said: Abd al-A’la narrated to us, from Ibn Ishaq, from Ubayd Allah ibn al-Mughirah ibn Mu’ayqib, who said—and he used to seek understanding—he said: Someone whom I do not accuse from my family narrated to me that he saw Mu’ayqib with his forelock let down between his eyes, and he saw Sa’d ibn Malik likewise.