Thank you for the question, “Are Paul’s letters applicable for us today? In what particular situations?”
The Apostle Paul states that ALL Scripture is beneficial for every generation of believers and for every believer. It is not applicable to non-believers since without a regeneration and transformation of life, the purposes and principles of Scriptures will not be relevant or applicable to them.
II Timothy 3 says this of believers, “But as for you, continue in what you have learned and have become convinced of, because you know those from whom you learned it, 15 and how from infancy you have known the Holy Scriptures, which are able to make you wise for salvation through faith in Christ Jesus. 16 All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, 17 so that the servant of God may be thoroughly equipped for every good work” (A searchable online Bible in over 150 versions and 50 languages). Bible citations are in the New International Version.
The Apostle Paul states that there are four fold application of Scriptures: teaching, rebuking, correcting, and training in righteousness. The purpose of the Scriptures is to fully complete a follower of Jesus for every good work, not just some good works. Believers may not be aware of certain teachings of Jesus. Believers may be living in disobedience to the Scripture of unforgiveness and wanting revenge. Other believers are not to tolerate sinful attitude and actions. Those attitude and actions must be pointed out in that person’s life. That is rebuking. Believers may need correction of incorrect teaching or manner of life. That person is stating or doing something that is not proper out of more ignorance than intentional wrong doing. Training in righteousness is being mentored by another believer in how to live a life that is pleasing to God. While believers live on earth, they are to do good works that glorify God.
As one reads the letters of the Apostle Paul, they are very relevant in our self-centered world. He says this in Ephesians 4, “So I tell you this, and insist on it in the Lord, that you must no longer live as the Gentiles do, in the futility of their thinking. 18 They are darkened in their understanding and separated from the life of God because of the ignorance that is in them due to the hardening of their hearts. 19 Having lost all sensitivity, they have given themselves over to sensuality so as to indulge in every kind of impurity, and they are full of greed.
20 That, however, is not the way of life you learned 21 when you heard about Christ and were taught in him in accordance with the truth that is in Jesus. 22 You were taught, with regard to your former way of life, to put off your old self, which is being corrupted by its deceitful desires; 23 to be made new in the attitude of your minds; 24 and to put on the new self, created to be like God in true righteousness and holiness.
25 Therefore each of you must put off falsehood and speak truthfully to your neighbor, for we are all members of one body. 26 “In your anger do not sin”: Do not let the sun go down while you are still angry, 27 and do not give the devil a foothold. 28 Anyone who has been stealing must steal no longer, but must work, doing something useful with their own hands, that they may have something to share with those in need. 29 Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen. 30 And do not grieve the Holy Spirit of God, with whom you were sealed for the day of redemption. 31 Get rid of all bitterness, rage and anger, brawling and slander, along with every form of malice. 32 Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you” (NIV).
It is easy to let unwholesome speech comes from one’s mouth to tear another person down, but it is truly hard to speak words that builds other up. The filthy words that may come forth from one’s mouth, it is because one has been injured by another person. The seething of that emotional hurt leads to bitterness, rage, anger, slander and may include murder. God calls his people to be kind and compassionate, forgiving others just as God has forgiven them.
Wouldn’t our family and community be better if we were able to apply the words of the Apostle Paul in our relationships? Nearly everyone would agree those are great values and actions. Knowing them and living them are two different things. Many of us can fulfill some or even most of them by our own strength, but few or none can consistency do it all the time. That is only possible with the enablement of the Holy Spirit. It is more than becoming other-centered than self-centered. For Christians, it is become Christ-centered.
SUMMARY: The Scriptures are given to encourage believers to live a Spirit filled life through Jesus Christ to the glory of God.
For more perspectives:
https://www.quora.com/Are-Paul-s-letters-applicable-for-us-today-In-what-particular-situations