When a non-believer becomes Muslim, should he pronounce the two testimonies of faith, al-shahaadatain, or perform wudu' (ablution) first?
He should say al-shahaadatain first, then he should purify himself for Salat and he can perform ghusl (complete bath) because the prophet ﷺ (peace and blessings of Allah be upon him) ordered some of his companions to perform it when they accepted Islam.