A.T. Robertson Commentary Matthew 26:35

"Peter saith unto him, Even if I must die with thee, [yet] will I not deny thee. Likewise also said all the disciples." — Matthew 26:35 (ASV)

Even if I must die with thee (κ ν δεη με συν σο αποθανειν). Third-class condition. A noble speech and meant well. His boast of loyalty is made still stronger by ου μη σε απαρνησομα. The other disciples were undoubtedly embarrassed by Peter's boast and lightheartedly joined in the same profession of fidelity.