He thanked the president and spontaneously reached over to shake his hand.
Ahmed said many people would not understand his gestures.
"I did not think about politics at all, I'm not a politician," he explained.
"I was totally focused on one issue, religious freedom.
President Donald Trump shakes hands with Farid Ahmed in the Oval Office. Photo / Supplied
"The whole world is affected either directly or indirectly by religious persecution - whether it is a bombing in Sri Lanka, shootings at a synagogue or mosque - it influences us all.
"I want people to come together, I want harmony and I was not thinking about other things."
He said there were certainly many things he and Trump would not agree on, but his purpose in travelling to the US was not to table those.
"I believe even his followers will be able to see that we are both humans who shook hands with one another and we had no bad feelings ... I thought that little gesture would be so positive.
"That day there were things we agreed on and those things should be encouraged and celebrated, there should not be any barriers.
"If you create barriers, how can you work in this world?"
The day after meeting Trump, Ahmed was selected to speak to US Secretary of State Mike Pompeo.
Christchurch terror survivor Farid Ahmed (R) meets US Secretary of State Mike Pompeo.
"I spoke about my experience, but I spoke about how New Zealand reacted and how together we are sharing our grief," he said.
"My story was positive and did not spend too much time describing the horrific things that happened - I focused on how can other people learn from the way we reacted together and what other lessons can we learn."
Ahmed said he was "overwhelmed" at how his message of positivity, forgiveness and unity was received in the US.
He said he had queues of people wanting to meet him and commend him for sharing his message, and to praise the New Zealand reaction to the shooting and Muslim community.
Ahmed said the trip was physically and mentally exhausting, but he was willing to sacrifice his health for the greater good.
The greater good was also helping him heal.
And, he was inspired by Husna - who passionately believed and taught about forgiveness and unity.
"When you focus on yourself you grieve more, but when you extend the circle bigger and you start to think about the other people affected it becomes easier to deal with," he said.
"Right from the beginning I didn't focus on my own grief, even when the shooting was happening and I went back in I was thinking bigger.
"This is also Husna's message."
Husna Ahmed - a woman with a big heart and message
Husna Ahmed was killed in the March 15 terror attacks in Christchurch.
Ahmed suffered severe injuries when he was hit by a car driven by a drink-driver in 1998.
He was airlifted from Nelson to Christchurch Hospital with near-fatal injuries and Husna was told there was 93 per cent chance he would die.
"My condition was terrible, the doctor told her 'he's not going to survive'," he explained.
