Al-Kāfi
Hadith 13293- وَبِإِسْنَادِهِ قَالَ قَالَ رَسُولُ اللهِ (صَلَّى اللهُ عَلَيْهِ وَآلِه) أَنْكِحُوا الأكْفَاءَ وَانْكِحُوا فِيهِمْ وَاخْتَارُوا لِنُطَفِكُمْ.
3. Through the same chain of narrators as that of the previous Hadith the following is narrated: “The Messenger of Allah has said, ‘Get married but the party must be a proper match, so marry from them (proper matches) and choose (proper environment) for your seeds.’”