Acts 2:39

For the promise [of forgiveness and the Holy Spirit] is being given to you [Jews] and to your descendants and [also] to all those who are far away [i.e., Gentiles. See Eph. 2:17]. [This promise is] to as many as [respond to] the Lord, our God's call [through the Gospel, See II Thess. 2:14]."

Acts 3:25-26

You people are descendants of these prophets and [recipients] of the Agreement God made with your forefathers when He said to Abraham [Gen. 12:3], 'And through your seed [i.e., your descendant Jesus] all the people of the earth will receive the blessings [of God].'

Romans 4:16

For this reason, the promise [i.e., of being made right with God] comes through faith [in God], according to His unearned favor, so that it may be [given] with certainty to all of Abraham's descendants. The promise is given not only to those [who live] under the law [i.e., the Jews], but also to [all] those [who live] by faith, like Abraham. Abraham is the [spiritual] father of all of us [believers],

Romans 9:7-8

Neither are all [Jewish] people children [of God], [simply] because they are Abraham's descendants. But [Gen. 21:12 says], "It is through Isaac that you [i.e., Abraham] will have descendants."

1 Corinthians 15:58

Therefore, my dearly loved brothers, stand firm [in the faith]; do not be moved [from your commitment]. Always do your best to work for the Lord, since you know that your labor in the Lord's [service] is not for nothing.

Galatians 3:29

And if you belong to Christ, then you are [truly] Abraham's seed [i.e., his spiritual descendants] and thereby [you will] inherit what was promised to him [i.e., God's blessings].

Treasury of Scripture Knowledge

Summary

They shall not labour in vain, nor bring forth for trouble; for they are the seed of the blessed of the LORD, and their offspring with them.

Bible References

Shall

1 Corinthians 15:58
Therefore, my dearly loved brothers, stand firm [in the faith]; do not be moved [from your commitment]. Always do your best to work for the Lord, since you know that your labor in the Lord's [service] is not for nothing.

For

Acts 2:39
For the promise [of forgiveness and the Holy Spirit] is being given to you [Jews] and to your descendants and [also] to all those who are far away [i.e., Gentiles. See Eph. 2:17]. [This promise is] to as many as [respond to] the Lord, our God's call [through the Gospel, See II Thess. 2:14]."
Acts 3:25
You people are descendants of these prophets and [recipients] of the Agreement God made with your forefathers when He said to Abraham [Gen. 12:3], 'And through your seed [i.e., your descendant Jesus] all the people of the earth will receive the blessings [of God].'
Romans 4:16
For this reason, the promise [i.e., of being made right with God] comes through faith [in God], according to His unearned favor, so that it may be [given] with certainty to all of Abraham's descendants. The promise is given not only to those [who live] under the law [i.e., the Jews], but also to [all] those [who live] by faith, like Abraham. Abraham is the [spiritual] father of all of us [believers],
Romans 9:7
Neither are all [Jewish] people children [of God], [simply] because they are Abraham's descendants. But [Gen. 21:12 says], "It is through Isaac that you [i.e., Abraham] will have descendants."
Galatians 3:29
And if you belong to Christ, then you are [truly] Abraham's seed [i.e., his spiritual descendants] and thereby [you will] inherit what was promised to him [i.e., God's blessings].