Romans 10:1-4

Paul shared a passionate desire that the Jews would be saved when he wrote these words in Romans 10:1-4 under the inspiration of the Holy Spirit:

Brethren, my heart’s desire and my prayer to God for them [Jews] is for their salvation. For I testify about them that they have a zeal [sincerity, good intentions] for God, but not in accordance with knowledge [the truth of God’s word]. For not knowing about God’s righteousness and seeking to establish their own, they did not subject [come to be subject] themselves to the righteousness of God. For Christ is the end of the law for righteousness to everyone who believes. 

This term believe is a popular word these days. You can go to Walmart and buy necklaces and bracelets and wall hangings with the words faith, believe, trust, etc. etc.
The thing is however, the people [Jews] Paul mentions in this passage are believers. They have a lot of faith, they are very sincere. The question is in what are they trusting? They had zeal but not according to knowledge or the truth. They even knew the Old Testament Scriptures but instead of allowing the Scriptures to be authoritative and point to the Writer and Author, they used the Scriptures to establish their own righteousness.
They had the Word of God, they believed it but their faith/belief was wrong.
How sad to be so close and yet so far. To have the truth in their very hands and to hold it in such high esteem yet totally miss the mark.
Zeal and intent are not good enough to attain righteousness. Being a good person is simply not good enough – ever.
So belief, really is only as effective as the object. I can believe with all my heart that I can fly. Yet if I jump off my roof, I will quickly realize I am powerless to do so (thank goodness the snow is deep-haha).
In salvation, belief is the same. To trust anything other than the power of God unto salvation is going to come crashing down in vain intent.
Many people will admit to being believers. When you ask what they believe, you may be surprised to hear the answer. Make sure you know your friends have the Gospel as the object of their faith. The Gospel is not merely believing Jesus is Lord or Jesus is God, it is resting your eternal salvation on the fact that Jesus died for your sins and rose again – there is no other gospel that can save (Rom 1:16).