Zayd bin Jubayr said: I was with Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) when he was asked about this, that is, someone on whom Hajj is obligatory and who vows a Hajj. He said: This is the obligatory Hajj of Islam; let him seek to fulfil his vow.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8691
Zayd bin Jubayr (may Allah have mercy on him) said: I heard a woman asking Sayyiduna Ibn Umar (may Allah be pleased with them both): I vowed to perform Hajj, while I have not performed the obligatory Hajj either. He said: First perform the obligatory Hajj! She said: I am poor and needy; pray to Allah Almighty for me. So he prayed that Allah Almighty make it easy for her.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8692
Anas bin Malik (may Allah be pleased with him) said, regarding someone who has vowed to perform Hajj and has not yet performed the obligatory Hajj: He should perform the obligatory Hajj first.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8693