Why did Jesus send his disciples out
two by two to preach the gospel?

Q. Why did Jesus send his disciples in pairs (Mark 6:7) to preach the gospel ?

A. To answer your question – I find just one reason for Christ sending them out in twos, is, they’re to be witnesses together.

"For where two or three are gathered together in My name, I am there in the midst of them.” (Matthew 18:20, NKJV throughout)

"And He called the twelve to Himself, and began to send them out two by two, and gave them power over unclean spirits." (Mark 6:7)

Note that in Mark 6:7 not only was Christ with them in Spirit – He gave them His Spiritual power to do His work!

The apostles were called not only to be Jesus' companions but also to be his witnesses to all of His teachings, miracles, etc. They were called and chosen to give a first-person testimony about Jesus' whole ministry.

Jesus' disciples were sent out by twos so that together they could be witnesses as to whether those who heard them accepted or rejected the gospel. If they went out alone one person’s word without a witness would not be acceptable in the things of God.

"Let two or three prophets speak, and let the others judge." (1Corinthians 14:29)

"This will be the third time I am coming to you. 'By the mouth of two or three witnesses every word shall be established.' " (2Corinthians 13:1)

The word of one person is not enough to establish the validity of anything!

"Do not receive an accusation against an elder [elderly person in the body of Christ, or any elderly person of society] except from two or three witnesses." (1Timothy 5:19)

"Anyone who has rejected Moses’ law dies without mercy on the testimony of two or three witnesses." (Hebrews 10:28)

"Also He [Jesus] said to them, 'In whatever place you enter a house, stay there till you depart from that place. And whoever will not receive you nor hear you, when you depart from there, shake off the dust under your feet as a testimony against them. [Christ was not speaking of just one household but of the people of a city or town here]

"Assuredly, I say to you, it will be more tolerable for Sodom and Gomorrah in the day of judgment than for that city!' So they went out and preached that people should repent. And they cast out many demons, and anointed with oil many who were sick, and healed them." (Mark 6:10-13)

The phrase "shake off the dust under your feet as a testimony against them" is similar in meaning to what God said to Israel in Deuteronomy 30:19. The shaking of dust from their [the disciples'] feet symbolized that even the earth (the dust on their feet) was a witness against a particular house or city:

"I call heaven and earth as witnesses today against you, [A witness against them.] that I have set before you life and death, blessing and cursing; therefore choose life, that both you and your descendants may live;" (Deuteronomy 30:19)