Do we need to seek forgiveness for sin after we are "saved"?
Romans 8:1 There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
To be ‘in Christ’ we must believe the gospel repent of our sinful way of life and be baptised into him by immersion in water.
Galatians 3:27 For as many of you as have been baptized into Christ have put on Christ.
Baptism into Christ washes away our past sins
Acts 2:38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins…
Acts 22:16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
After baptism we begin a new life.
Romans 6:4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
This new life must be lived by the commandments of Jesus Christ.
John 15:14 Ye are my friends, if ye do whatsoever I command you.
The commandments of Christ are ‘spirit’.
John 6:63 It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.
To live by the commandments of Christ is to walk ‘after the spirit’.
Two ways of life are contrasted:
The ‘flesh’ - doing what we want, and the ‘spirit’ – doing what Jesus commands us.
Galatians 5:19 Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness, 20 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies, 21 Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God. 22 But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, 23 Meekness, temperance: against such there is no law. 24 And they that are Christ’s have crucified the flesh with the affections and lusts.
The wages of sin is death.
Romans 6:23 For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.
Those who live sinfully are condemned while they live. Those who are baptised into Christ and are making a determined effort to live by his precepts are not condemned, but are promised forgiveness for their sins.
John 3:18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
After baptism we cannot live a sinless life but we are promised forgiveness of sins by confession in prayer.
1 John 1:7 But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. 8 If we say that we have no sin, we deceive ourselves, and the truth is not in us. 9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
To ‘walk in the light’ and ‘walk in the spirit’ both mean to live by the commandments of Christ.
Luke 6:46 And why call ye me, Lord, Lord, and do not the things which I say? 47 Whosoever cometh to me, and heareth my sayings, and doeth them, I will shew you to whom he is like: 48 He is like a man which built an house, and digged deep, and laid the foundation on a rock: and when the flood arose, the stream beat vehemently upon that house, and could not shake it: for it was founded upon a rock. 49 But he that heareth, and doeth not, is like a man that without a foundation built an house upon the earth; against which the stream did beat vehemently, and immediately it fell; and the ruin of that house was great.
If we live by the commandments of Christ we are not condemned and will be raised from the dead to eternal life when Christ returns.
John 6:40 And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day.
I hope you find this helpful.