This one, which is in many books and on many websites, struck me as immediately suspicious:
It would be true to say that loving kindness and compassion is all of our practice.
It’s also seen as:
It would be true to say that the cultivation of loving kindness and compassion is all of our practice.
Although lovingkindness (metta) and compassion (karuna) are important qualities, they by no means encompass the whole of Buddhist practice. Metta and karuna are part of the four “brahma-viharas,” or Divine Abidings, and so they only form half of the practices found in the context in which they’re most commonly listed together.
Whether it originated there or not, the popularity of this quotation goes back to an entry in Wikipedia, which has now been removed, although it still shows up in the site’s edit history:
Compassion or karuna is at the transcendental and experiential heart of the Buddha’s teachings. He was reputedly asked by his personal attendant, Ananda, “Would it be true to say that the cultivation of loving kindness and compassion is a part of our practice?” The Buddha replied, “No. It would not be true to say that the cultivation of loving kindness and compassion is part of our practice. It would be true to say that the cultivation of loving kindness and compassion is all of our practice.”
This fuller passage reveals this quotation to be a mis-translation or misinterpretation of a famous teaching:
I have heard that on one occasion the Blessed One was living among the Sakyans. Now there is a Sakyan town named Sakkara. There Ven. Ananda went to the Blessed One and, on arrival, having bowed down to the Blessed One, sat to one side. As he was sitting there, Ven. Ananda said to the Blessed One, “This is half of the holy life, lord: spiritual friendship (kalyāṇamittatā), spiritual companionship (kalyāṇasahāyatā), spiritual camaraderie (kalyāṇasampavaṅkatā).”
“Don’t say that, Ananda. Don’t say that. Spiritual friendship, spiritual companionship, spiritual camaraderie is actually the whole of the holy life. When a monk has admirable people as friends, companions, and comrades, he can be expected to develop & pursue the noble eightfold path. [Samyutta Nikaya (adapted)]
Spiritual friendship is considered to be so important because association with those with well-developed spiritual qualities can both support and challenge us, keeping us on the path. Lovingkindness and compassion are certainly part of the practice of spiritual friendship, but those two qualities were not the topics of the Buddha’s “whole of the spiritual life” statement.
Unfortunately Wikipedia’s misinformation sat unchallenged for many years (at least 2008—2014), which has resulted in it being widely promulgated.