Pope Francis on Thursday wished his predecessor Benedict XVI many happy returns on his 88th birthday and asked God to give him "support, much joy and happiness".
"Today is [Emeritus] Pope Benedict XVI's birthday and I have celebrated mass for him and invite you also to pray to God to give him support, much joy and happiness," Francis said, quoted by Vatican Radio.
Catholic Cardinals elected Francis Pope in March 2013, a month after Benedict became the first Pope in 600 years to abdicate. He was elected pontiff less than eight years earlier on 19 April, 2005.
Benedict said he was resigning as leader of the world's 1.3 billion Catholics owing to "lack of strength of mind and body" due to his advanced age.
Benedict's papacy was hit by scandal, notably the sexual abuse of children by priests - the worst storm the Church had faced in decades - and damaging claims that it was complicit in covering up many of the cases.
The former pontiff now lives in a restored convent inside the Vatican gardens, where is said to spend his retirement in prayer and meditation.
A former theology professor, Benedict has not written any theological works since his resignation, his personal secretary said this week.
