Jesus was constantly amazed at peoples' faith, lack of faith ,doubts and unbelief. He told those who doubted his words to believe in the miraculous works if they just couldn't accept what he told them.  He said that all the things he did and said were given to him by his father who is God and that he and the father are one - clearly claiming to be God himself.  Even his disciples which he hand picked -  lacked faith, doubted, forsook and one even betrayed him to his enemies. So why would they follow him if they were not fully convinced of who he said he was and risk the danger of being called his disciple? What happened that finally convinced those who followed Jesus, that he was God and that believing in him would save them from sin and gain them entrance into heaven ? It was an act of God's grace upon which they placed their faith. This grace which is God's unmerited favor is confirmed, sealed and empowered by the Holy Spirit which all true believers receive. So, once received the new believer now has the convincing proof of his conversion residing within him or her. The Holy Spirit of God is the witness to our faith and the power to become children of God. Placing your faith in Jesus is accepting God's offer of redemption, love and his eternal blessing upon your life. Placing your faith in anything else is to reject his offer and be eternaly condemned.  Their are many paths to Jesus but their is only one way to God and that is through Jesus who died, was  buried, resurrected and ascended to Heaven and now sits next to his Father. He has cleared the path and showed us The Way.
Doug L