"Rahul Gandhi's leadership has commenced during the most challenging times. But this will only make him stronger. Today, I will relinquish my responsibility with gratitude," she said after handing the charge of party to Rahul.
Sonia said Rahul has faced a lot of criticism from the Opposition since the time he made his debut in the national politics, but all these thing has only made him better.
"Rahul is my son, so I do not think for me to praise him is right but I would say that since childhood he had to bear the brunt of violence and after joining politics, he had to face blatant personal attacks that have made him a stronger person," she added.
Sonia said since 2014, the Congress has been playing the role of Opposition and the "challenge being faced today is the biggest one".
"Our constitutional values are being attacked, our party has also lost many elections but our party will never bow down. We all know how the values of our democratic and secular nation are under attack. This is an ethical fight. We should be ready to sacrifice anything for this," she said.
Recalling former prime minister and former Congress president Indira Gandhi, Sonia said, "Just seven years after Indira ji's assassination, my husband was assassinated too. My pillar of support was taken away and it took me long to come to terms with it."
"Twenty years ago, when I was elected as Congress President, I was nervous about this new role. I was anxious on how to uphold the heritage of the party. I became part of this family during revolutionary times," she added.
Her husband and former prime minister Rajiv Gandhi was assasinated in 1991. She took over as the party chief after his death.