Nafi' (may Allah have mercy on him) said that a man asked Sayyiduna Abdullah bin Umar (may Allah be pleased with them both): I pray in my house, then the prayer is being held in congregation; should I pray with the imam? Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: Yes, pray with the imam. He said: Which of the two should I make my obligatory prayer? Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: Is that up to you? That is from Allah; He makes obligatory whichever He wills.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3649