Muhammad bin Sa'd (may Allah have mercy on him) said that Sayyiduna Sa'd bin Abi Waqqas (may Allah be pleased with him) said: "I took part in the battle of Badr when there was nothing on my face but a single hair (of beard); then after that Allah Almighty made beards grow abundantly."
Imam al-Tabarani (may Allah have mercy on him) said: "Only Ibrahim bin al-Mundhir narrated this hadith from Ishaq bin Ja'far."
Hadith Referenceالمعجم الأوسط / باب الميم / 9139
Hadith Takhrij«أخرجه البزار فى «مسنده» برقم: 1104»