1) NAS Mark 14:38 "Keep watching and praying, that you may not come into
    temptation; the spirit is willing, but the flesh is weak."

Application: The weak believer needs to learn how to battle their flesh (the nature to
sin).  See Romans 7:21-25 and 6:19.  Compare the “weak women” in 2 Timothy
3:6.  Compare “sympathize with our weaknesses” in Hebrews 4:15-16.

2) NAS Romans 4:19 And without becoming weak in faith. . . 4:20 yet, with respect
    to the promise of God, he did not waver in unbelief, but grew strong in faith,

Application: The weak believer needs to strengthen their faith by learning and
believing the promises of God.

3) NAS Romans 14:1 Now accept the one who is weak in faith, but not for the
    purpose of passing judgment on his opinions. 2 One man has faith that he may eat
    all things, but he who is weak eats vegetables only. 3 Let not him who eats regard
    with contempt him who does not eat, and let not him who does not eat judge him
    who eats, for God has accepted him.

Application: Weak or strong, stop judging other believers. Later in the context,
Romans 14:19 and 15:14 state that believers should pursue mutual edification.  The
strong believer should increase the strength of the weak believer through teaching.
Note “help the weak” in 1 Thessalonians 5:14.

4) NAS 1 Corinthians 8:7 However not all men have this knowledge; but some, being
    accustomed to the idol until now, eat food as if it were sacrificed to an idol; and
    their conscience being weak is defiled.

Application: The weak believer needs to learn the Biblical truths that will overcome
their spiritual weaknesses.  See the previous context of 1 Corinthians 8:4-6.

5) NAS Galatians 4:9 But now that you have come to know God, or rather to be
    known by God, how is it that you turn back again to the weak and worthless
    elemental things, to which you desire to be enslaved all over again?

Application: Weak believers need to learn to not mix religion with the Biblical
Christianity. Note the next verse: (4:10) “You observe days and months and seasons
and years.”

6) NAS Hebrews 7:18 For, on the one hand, there is a setting aside of a former
    commandment because of its weakness and uselessness

Application: Some believers are weak because of dispensational misunderstanding.