Contradiction with Matthew 6:1
John 5:15 shows someone publicly declaring a miracle of Jesus, while Matthew 6:1 advises against public displays of piety and righteousness.
Matthew 6:1: Take heed that ye do not your alms before men, to be seen of them: otherwise ye have no reward of your Father which is in heaven. [alms: or, righteousness] [of your: or, with your]
Contradiction with Mark 1:44
John 5:15 involves spreading a miraculous work openly, whereas Mark 1:44 records Jesus instructing a healed man to keep the miracle private.
Mark 1:44: And saith unto him, See thou say nothing to any man: but go thy way, shew thyself to the priest, and offer for thy cleansing those things which Moses commanded, for a testimony unto them.
Contradiction with Matthew 8:4
John 5:15 involves declaring the miracle to all, opposed by Matthew 8:4, where Jesus advises to show oneself to the priest and keep the miracle otherwise quiet.
Matthew 8:4: And Jesus saith unto him, See thou tell no man; but go thy way, shew thyself to the priest, and offer the gift that Moses commanded, for a testimony unto them.
Contradiction with Mark 7:36
In John 5:15, the man tells others about Jesus, but Mark 7:36 illustrates Jesus instructing people not to spread word of his deeds.
Mark 7:36: And were beyond measure astonished, saying, He hath done all things well: he maketh both the deaf to hear, and the dumb to speak.
Contradiction with Luke 9:21
John 5:15 shows sharing of the miracle, contradicting Luke 9:21 where Jesus charged disciples to tell no one that He was the Christ.
Luke 9:21: And he straitly charged them, and commanded [them] to tell no man that thing;
Contradiction with Matthew 16:20
John 5:15 involves proclaiming Jesus' work, contrary to Matthew 16:20 where Jesus tells the disciples not to reveal He is the Christ.
Matthew 16:20: Then charged he his disciples that they should tell no man that he was Jesus the Christ.
Contradiction with Mark 8:30
The act in John 5:15 is in contrast with Mark 8:30, where Jesus charges the disciples to keep His identity a secret.
Mark 8:30: And he began to teach them, that the Son of man must suffer many things, and be rejected of the elders, and [of] the chief priests, and scribes, and be killed, and after three days rise again.
Contradiction with Luke 5:14
The instruction in John 5:15 to spread news contrasts with Jesus' order in Luke 5:14 to tell no one except the priest about the healing.
Luke 5:14: And he charged him to tell no man: but go, and shew thyself to the priest, and offer for thy cleansing, according as Moses commanded, for a testimony unto them.
Contradiction with Matthew 9:30
While John 5:15 promotes spreading the word, in Matthew 9:30, Jesus strictly charges those healed not to disclose it.
Matthew 9:30: And their eyes were opened; and Jesus straitly charged them, saying, See [that] no man know [it].
Contradiction with Mark 5:43
John 5:15 describes sharing news of His miracle, unlike Mark 5:43, where Jesus commands that it should not be known.
Mark 5:43: And he charged them straitly that no man should know it; and commanded that something should be given her to eat.