Q:  Jesus said, “And every one that hath forsaken houses or brethren, or sisters, etc., shall receive an hundredfold, and shall inherit everlasting life.”  If it is necessary to do this to inherit everlasting life, is that not salvation by works?  Aren’t there many who have not done this, and will therefore not inherit everlasting life?

A: For context I will quote Matthew19:27-29, in the AV: 

“Then answered Peter and said unto him, Behold, we have forsaken all, and followed thee; what shall we have therefore?  And Jesus said unto them, Verily I say unto you, That ye which have followed me, in the regeneration which the Son of man shall sit in the throne of his glory, ye also shall sit upon twelve thrones, judging the twelve tribes of Israel.  And every one that hath forsaken houses, or brethren, or sisters, or father, or mother, or wife, or children, or lands, for my name's sake. shall receive an hundredfold, and shall inherit everlasting life.”

Jesus earthly ministry was to His own people, Israel.  He preached to them the good news that the kingdom of the heavens was at hand. But only a small number believed and followed him. These were the “sheep who would hear his voice,” he being the shepherd.  Their hope, as was all Israel, was the reign of the Messiah in the coming kingdom on earth, which is the coming age or eon.

This era Jesus, in verse 28, calls “the regeneration.”  Peter, in Acts 3:19 refers to it as “the times of refreshing,” and in verse 21, “the times of restitution.”

Now, paraphrasing the questions: Since the followers of Jesus who have forsaken family and lands, will be receive an hundredfold and inherit everlasting life, is not this salvation by works?

A1)  Verse 29 must be read in context as shown above. The promised reward is to be “in the regeneration,” the coming millennial age, when Christ, the Son of man, sits in the throne of His glory. He told the 12 they would judge the 12 tribes of Israel. And in my option, only those of His disciples during His earthly ministry, and during the Acts period when the kingdom was reoffered to Israel, will be “the followers” Jesus referred to. And even though they may have forsaken family and lands, certainly their hearts were changed, so it is not just by works.

If you have access to a concordance, you will see that “everlasting” is an interpretation, not an accurate translation of the Greek originals.  From Young’s Literal Translation, it reads:

“..and everyone who left....for my name’s sake, an hundredfold shall receive, and life age-during shall receive.” Actually, life is promise for all the coming ages.

Q2)  During Jesus ministry, we know that only a few were true disciples, for during the ten days after his resurrection, we are told that he appeared to the twelve and upwards of 500. The vast majority of Israel rejected Jesus and they will be resurrected for judging at the Great White Throne. And, after Christ Jesus judges each one righteously according to his deeds, those whose names are not in the book of life will be throne into to the lake of fire, which is the second death. In other words, they die again. 

Is this their end? Yes, until the consummation of the eons, when all enemies have become subject to Christ, whether in the heavens or on the earth; the last enemy to be done away with is death. Which means all the dead will be resurrected to life to join the living, throughout the universe (See I Corinthians 15:22-28). And then, as we read in Philippians 2:9-11, “That in the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father.”