42 Jesus said to them, "If God were your Father, you would love me, for I came from God and now am here. I have not come on my own; but he sent me. 43 Why is my language not clear to you? Because you are unable to hear what I say. 44 You belong to your father, the devil, and you want to carry out your father's desire. He was a murderer from the beginning, not holding to the truth, for there is no truth in him. When he lies, he speaks his native language, for he is a liar and the father of lies. 45 Yet because I tell the truth, you do not believe me! 46 Can any of you prove me guilty of sin? If I am telling the truth, why don't you believe me? 47 He who belongs to God hears what God says. The reason you do not hear is that you do not belong to God."I am constantly speaking with people who are "already saved" or who call themselves a "Christian". I have family who are Catholic, Mormon and Jehovah's Witnesses. All of them would tell me that they are children of God and are going to Heaven. If I press a little further, and ask if they are "born again", they don't want to be called that. I ask them what do they do with the scripture where Jesus says that unless you are born again, you will not see the Kingdom of Heaven. I ask them if they read their Bible daily. I ask them if they are involved in a fellowship of other believers, do they like to be around Christians. I ask them if they think Jesus Christ is God Himself.
The majority of these people might get yes for one of these questions, but the overwhelming answer for these questions is an absolute 'no'. They really avoid the conversations and want to get out of there quickly. The Christians I know love to talk about Jesus. They love to read their Bible and they would definitely tell you they are born again. The unsaved people I know, even those who are members of a denomination, go out of their way to avoid God. They don't hear Him because they do not belong to Him.
It is important not to just take someone's word that they are already a Christian when you are evangelizing. Many people know that if they tell you that, you will smile and walk away. Don't accuse anyone of anything, but press them politely. What a shame it would be if they are among the people who say, "Lord, Lord" but Jesus tells them that He never knew them.
Only God knows their heart, and I would never presume to tell anyone that they are saved or not saved... But, big red lights go off in my head when I hear of someone who tells me they are saved, but doesn't go near a Bible, doesn't set foot in a church, and really wants nothing to do with Jesus.