FIRST, what is religion? The basic thought of religion is the performance of duties. The word comes from the Latin root religio—a taboo or restraint—and is related to a word meaning, "to hold back, bind fast" (Webster), that is, to bind duties on a person.
There was only one religion given by God to man. It was the religion of the Jews as given to them under Moses, with all its observances and ritual. A person had to keep the whole law, since breaking one point of the law made the offender guilty.
Performance of religious duties may bring some a measure of satisfaction and may be done in hope of gaining some merit with God, but the Bible clearly says that salvation is NOT won through keeping the law or performing duties. By man's failure to keep it, the law of God condemned and sentenced all— everyone!—under sin, guilty before God.
If my religion will not bring salvation and peace with God, how may these be obtained? Christ Jesus by His sacrificial death on the cross bore the judgment of the law and so God can, righteously, offer pardon, peace and eternal life to all who believe.
Religion—our own efforts—is not enough. Only a personal faith in Christ Jesus as Savior gives assurance of salvation.