Ajahn Cunda reflects on Majjhima Nikāya 45, Cūḷa Dhamma-Samādāna Suttaṃ 45 (Lesser Discourse on the (Ways of) Undertaking Dhamma)
“These four, monks, are (ways of) undertaking Dhamma. What four? There is, monks, the undertaking of Dhamma that is happiness in the present but results in suffering in the future. There is, monks, the undertaking of Dhamma that is both suffering in the present as well as resulting in suffering in the future. There is, monks, the undertaking of Dhamma that is suffering in the present but results in happiness in the future. There is, monks, the undertaking of Dhamma that is both happiness in the present as well as resulting in happiness in the future.”
Full sutta can be found here: https://legacy.suttacentral.net/en/mn45