Bribery of the guards (peculiar to St. Matthew). The report of the soldiers may have had something to do with the conversion of so many priests described in Acts 6:7.
Related Commentaries of Matthew 28:11
Matthew 28:11-15
11 Now when they were going, behold, some of the watch came into the city, and shewed unto the chief priests all the things that were done.
12 And when they were assembled with the elders, and had taken counsel, they gave large money unto the soldiers,
13 Saying, Say ye, His disciples came by night, and stole him away while we slept.
14 And if this come to the governor's ears, we will persuade him, and secure you.
15 So they took the money, and did as they were taught: and this saying is commonly reported among the Jews until this day.