"I am shocked and deeply saddened at the sudden passing away of your beloved wife, Smt Sushma Swaraj," Gandhi said in a letter to late minister's husband Swaraj Kaushal.
"Sushma Swaraj was a lady of extraordinary gifts, her courage, determination, dedication and ability manifest in every position she held. Above all, it was her warm personal qualities that brought a special lustre to her years in public and political life. She made herself accessible to even the humblest person, established a warm rapport with people from all walks of life, and with her empathy and compassion, gave Indian diplomacy a human face as she reached out to help every Indian citizen in distress," Gandhi said.
She went on to say that Sushma Swaraj was a "superb orator, a great parliamentarian and had a rare gift for friendship that won her affection and admiration across the political spectrum."
"In our many years together as colleagues in the Lok Sabha, we developed a warm personal relationship and I feel her loss greatly. The same courage and grit that was a hallmark of Sushma-ji's political life, she showed in her personal life as well, as she faced her serious ailments with incredible fortitude. She has left us when she was far too young, when she had so much more to contribute to national life, and that makes her death even more tragic," Gandhi said.
She further added in her letter to Swaraj Kaushal, "At this time of grief, my thoughts and prayers are with you and your daughter Bansuri. May you find the strength to bear your cruel loss. You must draw solace from the fact that Sushmaji lived a life of honour, filled with achievement and contributions to the country she loved; respected and admired by all Indians. And she went as she had lived - active and engaged till the very end."
Swaraj passed away at AIIMS following a cardiac arrest on Tuesday night.
According to sources at AIIMS, the 67-year-old was feeling restless at 9 pm and reached the hospital at around 9:30 pm in an ambulance. She was declared dead at 10:50 pm.
Swaraj was appointed the foreign minister in the first term of Modi government in 2014. She opted out of the 2019 Lok Sabha elections citing health reasons.