Much of the Bible is written to believers in Christ to hold fast to our belief and confidence in Jesus Christ and Him only. Paul wrote to the Thessalonian believers to "therefore, brethren, stand fast, and hold to the traditions which ye have been taught whether by work or our epistle."
The apostle had come to be a Christian, a writer, and a missionary to them. According to his teachings there was no other way to get to know the Lord. What he had taught them was the truth and they should never ever turn away from the truth.
The bible says in John 6, he spoke the words of Jesus that there were some that had followed him that were followers but not true disciples for he knew their hearts. Some followed him that were not really true disciples but only followed him for the healings and provisions he made for them.
Some had followed as a result of the miracles of healing and some because they saw and were in on the miracles like feeding a great multitude and they wanted more of those things but wouldn't follow when his demands were put upon them. Salvation is free but discipleship is costly.
They would follow him for the wrong reason. You see the Lord truly knows whether it is faithful faith or just for some physical blessings.
The bible says in John 6:66 "From that time many disciples went back, and walked with him no more. They claimed to be disciples and followers but followed no more. These followers were not true followers like the twelve apostles for they stuck with Christ until their end. True disciples believe and are faithful unto death. One of them, Judas, failed and that was Judas Iscariot. Jesus said he was of the devil from the beginning.
The Lord knows if we are to be genuine apostles. Jesus asked the twelve apostles, "Will you go away also? Peter answered him, Lord, to whom shall we go? Thou hast the words of eternal life. For we believe and are sure that thou art the Christ, the son of the living God." Then he told them that one of them was not a true follower but would deny him.
So our effort is to believe and look not for any other for he is sufficient for all of life now and our eternal hope, is as promised in the Word of God.
I have read of some other religious writings but I have never ever considered their promises. I join the disciples in their confidence. Lord where else could I go or even consider.