Albert Barnes Commentary 1 Peter 1:14

"as children of obedience, not fashioning yourselves according to your former lusts in [the time of] your ignorance:" — 1 Peter 1:14 (ASV)

As obedient children. That is, conduct yourselves as is fitting for the children of God, by obeying his commands, by submitting to his will, and by manifesting unwavering confidence in him as your Father, at all times.

Not fashioning yourselves. Not forming or modelling your life. Compare to Romans 12:2.

The idea is that they were to have some model or example, in accordance with which they were to frame their lives, but they were not to make their own former principles and conduct the model. The Christian is to be as different from what he was himself before conversion as he is from others. He is to be governed by new laws, to aim at new objects, and to mould his life in accordance with new principles. Before conversion, he was:

• Supremely selfish;
• He lived for personal gratification;
• He gave free indulgence to his appetites and passions, restrained only by a respect for the decencies of life, and by a reference to his own health, property, or reputation, without regard to the will of God;
• He conformed himself to the customs and opinions around him, rather than to the requirements of his Maker;
• He lived for worldly ambitions, his supreme object being wealth or fame; or
• In many cases, those who are now Christians gave indulgence to every passion they wished to gratify, regardless of reputation, health, property, or salvation.

Now they are to be governed by a different rule, and their own former standard of morals and opinions is no longer their guide, but the will of God.

According to the former lusts in your ignorance. When you were ignorant of the requirements of the gospel, and gave yourselves up to the unrestrained indulgence of your passions.