1 John 2:29 - 3:6 / John 1:29-34
We may have heard of this term "a spiritual person". There can be many definitions and understandings to this term.
But generally speaking, the common expectation of someone who is "a spiritual person" is that he/she has got some spiritual gifts, eg. healing, miracles, prophecy, visionary, etc.
These manifestations are spectacular and may be associated with "a spiritual person". But a truly spiritual person may also be a rather common person that exhibits none of the above.
Nonetheless, by the life of the person, we will be able to see whether that person is essentially a spiritual person, just as a tree is judged by its fruits.
John the Baptist did not work any miracles of healing or give any spectacular signs. He only preached the Word of God as it came to him and he baptised people for the repentance of sins.
But he was someone who can be called a truly "spiritual person" because he was closely in touch with the promptings of the Spirit of God and it was he who pointed out Jesus as the Lamb of God who takes away the sins of the world. Literally, God spoke to him and told him who Jesus was.
The 1st reading gives another expression of what a truly spiritual person is - everyone whose life is righteous has been begotten by God.
That life of righteousness is lived out with a purity of life, a purity that is rooted in Jesus, a life that avoids sin.
So when we live a life of righteousness and purity, we will be able to "hear" what God is saying to us. And then by our lives and our words, people will know whether or not we are a spiritual person.