Johnson said during the three and a half years since people in Britain voted to leave the European Union, the whole experience had been so hard for the country and so divisive, with families across the country divided.
Johnson hopes for success in getting a fractious Parliament to back the deal after his predecessor, Theresa May, failed three times to get lawmakers behind her Brexit plan.
Johnson, who came to power in July vowing to get Brexit finished, called any delay to Britain's departure pointless, expensive and corrosive of public trust.
MPs voted by 322 to 306 to back a motion by former Conservative minister Oliver Letwin that "withholds approval (of the deal) unless and until implementing legislation is passed".
Mr Letwin's proposal, which has cross-party support, will be put to a vote at the end of Saturday's debate. But that could present opponents with an opportunity to try to amend his plan.
Amid noisy Commons scenes, Mr Johnson insisted he was not "daunted or dismayed" by the result and remained committed to taking Britain out by October 31.
Opposition parties and Johnson's own Northern Irish allies have rejected the text but the prime minister and his team have spent the past 48 hours frantically trying to win MPs' support.
The Conservative Party confirmed the PM's stance in a tweet.
One of the lawmakers behind the measure, Oliver Letwin, said it would prevent the United Kingdom from leaving at the end of the month "by mistake, if something goes wrong during the passage of the implementing legislation".
Johnson has said he will not do so, but government lawyers have told a court he plans to comply with the law. That would bring another law into play that would force Johnson to seek a Brexit delay from the European Union.
"Now it is urgent for us to move on, on the basis of the new deal to heal the rift in politics", he said. He spoke with a tone of gravity and conciliation that contrasted starkly with the inflammatory language he has used during previous parliamentary debates over Brexit.
Should he fail, Johnson will face the humiliation of Brexit unraveling after repeatedly promising that he would get it done - "do or die" - by October 31. Needing to avoid physical border checks, Mrs. It commits the country to very little alignment with the bloc on trade or regulations, turning its back on much of the web of rules that critics in Britain consider stifling or a threat to their sovereignty.
"Today we MPs (Members of Parliament) have the chance to free you from the never-ending Brexit saga and move this country forward", Mr Johnson wrote.
Leaving the European Union legally does not end the Brexit drama; it merely brings down the curtain on Act One.
A sea of protesters was across the street from Parliament when word arrived that lawmakers in the House of Commons had forced another delay in Britain's protracted Brexit battle. Parliament rejected her deal three times, by margins of between 58 and 230 votes earlier this year. The EU eventually agreed to postpone Brexit until Oct. 31; Johnson has previously the United Kingdom must leave the EU by the end of October - even if there's no deal in place that sets up the parameters of the divorce, like trade and the rights of European citizens living in the UK. He adds "I am British but I am also European".
At the same time, Brexit opponents became less inclined to settle on a compromise that they saw as the worst of both worlds.
Labour leaders have told party lawmakers to oppose the deal.
Some influential hardline Brexit supporters have said they will support the deal. The smaller and more pro-European Liberal Democrats say they would stay in the bloc without holding a second vote.
I promised a blog on what's coming up in Parliament next week, and indeed, it is more than half written; the trouble is, as outlined above, the agenda for next week will have to be reshaped.
Even though Johnson believes this can be achieved by October 31, others think it would need a short "technical" delay.