Matthew 27:51–53 English Standard Version
51 And behold, the curtain of the temple was torn in two, from top to bottom. And the earth shook, and the rocks were split.
52 The tombs also were opened. And many bodies of the saints who had fallen asleep were raised,
53 and coming out of the tombs after his resurrection, they went into the holy city and appeared to many.
According to Bible scholars, these people were dead (who know nothing) in the *Old Testament = Sleep. They were raised with “glorified” bodies (like Christ); just long enough for about 500 witnesses to see them, then went to paradise (Heaven) with the Lord.
New Testament believers are already connected spiritually to the Lord (if born again) and are immediately with the Lord when their bodies pack up. Jonathan Edwards (1700s) did the earliest writing on this. Paul said it, and I personally know when my heart stopped, Jesus was shoulder to shoulder against me! So Heaven is where the Saved goes prior to the final resurrection and judgment. Hell is also a “holding place” like a jail prior to sentencing, when we shall all stand before the Lord. These things are abundantly clear to me, (even scripturally) yet still, you will find all sorts of opinions in this area of study.