Some argue that the Bible is contradictory concerning whether the rooster crowed once or twice before Peter’s third denial. The argument is that Matthew 26:34, 74-75, Luke 22:34, 60-62 and John 13:38 say that the rooster crowed once, but Mark 14:30, 72 says that the rooster crowed twice. However, there is a reasonable explanation that solves this alleged contradiction in the Bible.
34 Jesus said to him, “Truly, I tell you, this very night, before the rooster crows, you will deny me three times.” … 74 Then he began to invoke a curse on himself and to swear, “I do not know the man.” And immediately the rooster crowed. 75 And Peter remembered the saying of Jesus, “Before the rooster crows, you will deny me three times.” And he went out and wept bitterly.
Matthew 26:34, 74-75
34 Jesus said, “I tell you, Peter, the rooster will not crow this day, until you deny three times that you know me.” … 60 But Peter said, “Man, I do not know what you are talking about.” And immediately, while he was still speaking, the rooster crowed. 61 And the Lord turned and looked at Peter. And Peter remembered the saying of the Lord, how he had said to him, “Before the rooster crows today, you will deny me three times.” 62 And he went out and wept bitterly.
Luke 22:34, 60-62
Jesus answered, “Will you lay down your life for me? Truly, truly, I say to you, the rooster will not crow till you have denied me three times.
John 13:38
30 And Jesus said to him, “Truly, I tell you, this very night, before the rooster crows twice, you will deny me three times.” … 72 And immediately the rooster crowed a second time. And Peter remembered how Jesus had said to him, “Before the rooster crows twice, you will deny me three times.” And he broke down and wept.
Mark 14:72
The most likely explanation for this alleged contradiction is that there were two different roosters that crowed, and the crows were separated by a long enough period of time that the second crow could also be grouped by itself.
Matthew, Luke, and John simply reference the second rooster that crowed, while Mark references both the first rooster that crowed earlier, as well as the second rooster that crowed immediately after Peter’s third denial.
It is also possible that there was a copyist error. Beza’s ancient copy that was given to Cambridge University, as well as the Ethiopic version, does not contain the word “twice” in Mark 14:30. ((John Gill, ”Commentary on the Bible”, notes Matthew 26:34, as adapted from Online Bible, by Larry Pierce.))
There are some foundational principles that apply to all alleged and apparent contradictions in the Bible. To read more, see Bible Difficulties: Foundational Principles.
To read more answers to alleged and apparent contradictions in the Bible, see “Contradictions” in the Bible Answered.
These books are also excellent resources:
Evidence That Demands a Verdict: Life-Changing Truth for a Skeptical World - Josh and Sean McDowell
Little Pilgrim's Progress (Illustrated Edition) - Helen L. Taylor