SB 3.25.22
mayy ananyena bhavena
bhaktim kurvanti ye drdham
mat-krte tyakta-karmanas
tyakta-svajana-bandhavah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Such a sadhu engages in staunch devotional service to the Lord without deviation. For the sake of the Lord he renounces all other connections, such as family relationships and friendly acquaintances within the world.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
A person in the renounced order of life, a sannyasi, is also called a sadhu because he renounces everything — his home, his comfort, his friends, his relatives, and his duties to friends and family. He renounces everything for the sake of the Supreme Personality of Godhead. A sannyasi is generally in the renounced order of life, but his renunciation will be successful only when his energy is employed in the service of the Lord with great austerity. It is said here, therefore, bhaktim kurvanti ye drdham. A person who seriously engages in the service of the Lord and is in the renounced order of life is a sadhu. A sadhu is one who has given up all responsibility to society, family, and worldly humanitarianism, simply for the service of the Lord. As soon as he takes his birth in the world, a person has so many responsibilities and obligations — to the public, to the demigods, to the great sages, to the general living beings, to his parents, to the family forefathers and to many others. When he gives up all such obligations for the sake of the service of the Supreme Lord, he is not punished for such renunciation of obligation. But if for sense gratification a person renounces all such obligations, he is punished by the law of nature.