Tradition affirms that both Saints Peter and Paul were martyred in Rome under the Roman Emperor Nero in the year 67. However, their martyrdoms probably did not occur on the same day, and this feast puts them together possibly for the translation of their relics, rather than for the feast of the martyrdom.
It is believed Peter was crucified and Paul was beheaded. According to the accounts of Ignatius of Antioch, Clement of Rome, and Irenaeus, Peter most likely sets up his apostolate in Rome following his governing of the Church in Jerusalem. Paul also preached in Rome, although this was toward the end of his ministry. In the Early Church, their martyrdoms were celebrated in the basilicas which had been built over their tombs
The Martyrdom of the Apostles Peter and Paul - 29 June
Almighty God, whose blessed apostles Peter and Paul glorified thee by their martyrdom: Grant that thy Church, instructed by their teaching and example, and knit together in unity by thy Spirit, may ever stand firm upon the one foundation, which is Jesus Christ our Lord; who liveth and reigneth with thee, in the unity of the same Spirit, one God, for ever and ever. Amen.
The Epistle - 2 Timothy 4:1-8.
I charge thee therefore before God, and the Lord Jesus Christ, who shall judge the quick and the dead at his appearing and his kingdom; Preach the word; be instant in season, out of season; reprove, rebuke, exhort with all long suffering and doctrine. For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears; And they shall turn away their ears from the truth, and shall be turned unto fables. But watch thou in all things, endure afflictions, do the work of an evangelist, make full proof of thy ministry. For I am now ready to be offered, and the time of my departure is at hand. I have fought a good fight, I have finished my course, I have kept the faith: Henceforth there is laid up for me a crown of righteousness, which the Lord, the righteous judge, shall give me at that day: and not to me only, but unto all them also that love his appearing.
The Gospel - St. John 21:15-19.
So when they had dined, Jesus saith to Simon Peter, Simon, son of Jonas, lovest thou me more than these? He saith unto him, Yea, Lord; thou knowest that I love thee. He saith unto him, Feed my lambs. He saith to him again the second time, Simon, son of Jonas, lovest thou me? He saith unto him, Yea, Lord; thou knowest that I love thee. He saith unto him, Feed my sheep. He saith unto him the third time, Simon, son of Jonas, lovest thou me? Peter was grieved because he said unto him the third time, Lovest thou me? And he said unto him, Lord, thou knowest all things; thou knowest that I love thee. Jesus saith unto him, Feed my sheep. Verily, verily, I say unto thee, When thou wast young, thou girdest thyself, and walkedst whither thou wouldest: but when thou shalt be old, thou shalt stretch forth thy hands, and another shall gird thee, and carry thee whither thou wouldest not. This spake he, signifying by what death he should glorify God. And when he had spoken this, he saith unto him, Follow me.
Reference and Resources: