1 Corinthians 11:28
So, a person should examine himself [first] and then he should eat the bread and drink from the cup.
James 5:15-16
And if their prayer is [offered] by faith, [God] will heal the one who is sick, and the Lord will raise him up [from his sickbed]. And if he had sinned, he will be forgiven for them [Note: This may imply that the man's sickness was the result of some sin. In any event, his forgiveness would follow his repentance].
1 John 5:16
If anyone [of you] observes his brother [or sister] sinning [in a way that would not lead] to [spiritual] death, he should ask [God, in prayer, to help that person], and God will give him [spiritual] life, [that is], to such ones, provided their sin is not leading to [spiritual] death. There is such a sin that leads to [spiritual] death. [See Heb. 6:4-6; I Tim. 5:6; Heb. 10:26-27; II Pet. 2:20-22]. I am not suggesting that you should ask [God, in prayer] about such a situation.