Yes he can be used as proof. So can Cornelius, he was saved b4 he was water baptized. It came after he was a confirmed believer in Christ Acts 10:43-48
43;To him give all the prophets witness, that through his name whosoever believeth in him shall receive remission of sins.
44 While Peter yet spake these words, the Holy Ghost fell on all them which heard the word.
45 And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost.
46 For they heard them speak with tongues, and magnify God. Then answered Peter,
47 Can any man forbid water, that these should not be baptized, which have received the Holy Ghost as well as we?
48 And he commanded them to be baptized in the name of the Lord. Then prayed they him to tarry certain days.
God had already saved Cornelius and them and had given them the Gift of the Holy Ghost, b4 water baptism.
The water baptism was a ritual to identify with the New Covenant Faith and other believers. But Cornelius was saved even b4 Peter preached to him, Peter realized that from Vs 34-35
34 Then Peter opened his mouth, and said, Of a truth I perceive that God is no respecter of persons:
35 But in every nation he that feareth him, and worketh righteousness, is accepted with him.