If he has not paid in cash he can return it and buy another.

If he has not paid in cash he can return it and buy another.’ Abu ‘Abd Allah (a.s.), has said, ‘Buy a fatty male for al-Hajj al-Tamattu‘ (advantageous); if you cannot, then find a mawju’ (cow); if you cannot find it then a male goat, if you do not find, then an ewe, if you cannot find then buy what is available for an offering.’ He (the Imam) said, ‘For al-Hajj al-Tamattu‘ (advantageous) young sheep is sufficient, a young goat is not sufficient.’ About a man who bought a sheep and wanted to buy one more fat, abu ‘Abd Allah (a.s.), has said, ‘He can buy it but he sells the first one.’ I do not know if he (the Imam) spoke of sheep or cow.”

حسن - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (18/165))