4:12 Beloved, don't be astonished at the fiery trial which has come upon you,
to test you, as though a strange thing happened to you.
4:13 But because you are partakers of Christ's sufferings, rejoice;
that at the revelation of his glory also you may rejoice with exceeding joy.

4:14 If you are insulted for the name of Christ, blessed are you;
because the Spirit of glory and of God rests on you.
On their part he is blasphemed, but on your part he is glorified.

4:15 For let none of you suffer as a murderer, or a thief,
or an evil doer, or as a meddler in other men's matters.

4:16 But if one of you suffers for being a Christian, let him not be ashamed;
but let him glorify God in this matter.
 

4:17 For the time has come for judgment to begin at the house of God.
If it begins first with us, what will happen to those
who don't obey the gospel of God?

4:18 "If it is hard for the righteous to be saved,
what will happen to the ungodly and the sinner?" (Prov 11:31)

4:19 Therefore let them also who suffer according to the will of God
in doing good entrust their souls to him, as to a faithful Creator.

vs 15-16 Just as Christ suffered not for his own sins, but for other peoples sin, so also Christians should strive to live sinlessly, while accepting a degree of suffering due to other people's sinfulness. A Christian should not feel ashamed for suffering as a Christian, but glory in God.

It mentions "meddlers" - he is one who takes the supervision of affairs pertaining to others and in no wise to himself, a meddler in other men's affairs. He meddles in things which should be none of his business. Gossiping is related to this also. 1 Timothy 5:13  "Besides, they get into the habit of being idle and going about from house to house. And not only do they become idlers, but also gossips and busybodies, saying things they ought not to." (niv)

vs 17-18 I think what Peter means by the expression "judgment must begin at the house of God" is that God tests the faith of Christians by bringing them through trials to reveal whether their faith is of salvific value. Under such trials either nominal Christians will fall away or develop their faith to the level of a conviction. In this case the "house of God" refers to the visible church composed of nominal Christians and those born of God. But while nominal Christians have a good chance to be saved, those who reject the gospel have a less likely chance to come to faith in Christ.

Saying the righteous are scarcely saved, or that they are saved with great difficulty, reveals Peter's perspective on salvation being a process. I often liken the development of saving faith to the people of Israel wandering in the Sinai desert, being subjected to humiliating circumstances and trials. (See "Becoming a Christian") The popular modern concepts of easy-believism and of the equating of assurance of salvation with saving faith in Christ are deviations from Biblical Christianity.

On the other hand there is a difference between entering into salvation and maintaining one's salvation status. One is difficult and the other is inevitable, being guaranteed. It may be difficult to win the lottery, but having won it, the rewards are guaranteed.

vs 19 We would all live the Christian life better and with more contentment if we all learn to give up our expectations to God. We should not expect the Christian life to be smooth sailing. For even if Jesus is in the boat as with his disciples, he could readily bring up the worst of storms just to test our faith. And while we struggle through it, God is asleep in the boat! In the next chapter Peter will also remind us to "Cast all your anxiety on him because he cares for you." 1Peter 5:7