Acts 2:1

And when the day of Pentecost came [Note: This was a Jewish festival held fifty days following the Passover Festival. Lev. 23:15-21], they [i.e., the twelve apostles] were all gathered together in one place [i.e., their second story living quarters, 1:13 ?].

Acts 20:16

For Paul had decided to sail on past Ephesus so he would not have to spend any time in [the province of] Asia, because he was hurrying to get to Jerusalem in time for the Day of Pentecost, if at all possible.

1 Corinthians 16:8

But I will wait [here] in Ephesus until the Day of Pentecost [Note: This was an annual Jewish festival, held at spring harvest time];

Acts 1:13-15

Upon arriving at the house where they were staying, they went upstairs. [Those present were]: Peter, John, James, Andrew, Philip, Thomas, Bartholomew, Matthew, James, the son of Alpheus, Simon the Zealous [one] and Judas, the son of James. [Note: Judas Iscariot, the twelfth apostle, had already committed suicide].

Acts 2:46

And every day they continued to meet together in the Temple [i.e., for teaching and worship]. They were enjoying their meals and the close fellowship they shared in the various homes, and were

Acts 4:24

And when the disciples heard this report they united their voices to God in prayer [saying]: "O, Lord, You made the heaven, the earth, the sea and everything in them.

Acts 4:32

So, the large number of believers were united in heart and soul [i.e., mind and spirit] and not one of them said that anything he owned [really] belonged to him, but they shared all things in common.

Acts 5:12

And many [miraculous] signs and wonders were performed through the apostles' hands in front of the people. And all [the disciples] were united together in "Solomon's Portico" [See 3:11].

Romans 15:6

so that in [genuine] unity and with one voice, you people may honor the God and Father of our Lord Jesus Christ.

Philippians 1:27

So, [whatever happens], live your daily lives in such a way as to be worthy of the Gospel of Christ, so that, whether I come and see you or remain absent from you, I will hear about you, that you are standing firm in one spirit [i.e., united in purpose, and] contending with one mind for the faith of the Gospel [i.e., for the body of Christian teaching].

Philippians 2:2

[Then] make me completely happy by being like-minded, having the same love [for one another], being united in spirit and having the same purpose.

Treasury of Scripture Knowledge

Summary

And when the day of Pentecost was fully come, they were all with one accord in one place.

General references

Bible References

The day

Acts 20:16
For Paul had decided to sail on past Ephesus so he would not have to spend any time in [the province of] Asia, because he was hurrying to get to Jerusalem in time for the Day of Pentecost, if at all possible.
1 Corinthians 16:8
But I will wait [here] in Ephesus until the Day of Pentecost [Note: This was an annual Jewish festival, held at spring harvest time];

They

Acts 2:46
And every day they continued to meet together in the Temple [i.e., for teaching and worship]. They were enjoying their meals and the close fellowship they shared in the various homes, and were
Acts 1:13
Upon arriving at the house where they were staying, they went upstairs. [Those present were]: Peter, John, James, Andrew, Philip, Thomas, Bartholomew, Matthew, James, the son of Alpheus, Simon the Zealous [one] and Judas, the son of James. [Note: Judas Iscariot, the twelfth apostle, had already committed suicide].
Acts 4:24
And when the disciples heard this report they united their voices to God in prayer [saying]: "O, Lord, You made the heaven, the earth, the sea and everything in them.
Acts 5:12
And many [miraculous] signs and wonders were performed through the apostles' hands in front of the people. And all [the disciples] were united together in "Solomon's Portico" [See 3:11].
Romans 15:6
so that in [genuine] unity and with one voice, you people may honor the God and Father of our Lord Jesus Christ.
Philippians 1:27
So, [whatever happens], live your daily lives in such a way as to be worthy of the Gospel of Christ, so that, whether I come and see you or remain absent from you, I will hear about you, that you are standing firm in one spirit [i.e., united in purpose, and] contending with one mind for the faith of the Gospel [i.e., for the body of Christian teaching].
Philippians 2:2
[Then] make me completely happy by being like-minded, having the same love [for one another], being united in spirit and having the same purpose.

General references

Hebrews 13:1
Continue to love [one another] as brothers.