There are too many scriptures that show the conditional nature of salvation to meaningfully review here. However, let's focus on one common thread in scripture: perseverance. Scripture teaches that it is those who persevere unto the end that are saved, that that which is promised to us is contingent upon this.
Hebrews 10:36 You need to persevere so that when you have done the
will of God, you will receive what he has promised.
1 Timothy 4:16 Watch your life and doctrine closely. Persevere in
them, because if you do, you will save both yourself and your hearers.
James 1:12 Blessed is the one who perseveres under trial because,
having stood the test, that person will receive the crown of life that
the Lord has promised to those who love him.
2 Timothy 4:6-8 For I am already being poured out like a drink
offering, and the time for my departure is near. 7 I have fought the
good fight, I have finished the race, I have kept the faith. 8 Now
there is in store for me the crown of righteousness, which the Lord,
the righteous Judge, will award to me on that day—and not only to me,
but also to all who have longed for his appearing.
Also, a bonus scripture - because I think it is very powerful at speaking to not just our responsibility to keep God's commands, but also to our personal ability to do so. To keep the commands is a choice with corresponding consequences/rewards:
Deutoronomy 30:11-16 Now what I am commanding you today is not too
difficult for you or beyond your reach. 12 It is not up in heaven, so
that you have to ask, “Who will ascend into heaven to get it and
proclaim it to us so we may obey it?” 13 Nor is it beyond the sea, so
that you have to ask, “Who will cross the sea to get it and proclaim
it to us so we may obey it?” 14 No, the word is very near you; it is
in your mouth and in your heart so you may obey it. 15 See, I set
before you today life and prosperity, death and destruction. 16 For I
command you today to love the Lord your God, to walk in obedience to
him, and to keep his commands, decrees and laws; then you will live
and increase, and the Lord your God will bless you in the land you are
entering to possess.