The Rebbe's guidance for people returning to Torah observance, and for those helping them:
Coming home to yourself. Returning to Torah is reclaiming one's true self; keep going through spiritual and financial challenges, because every effort invested now yields lasting fruit (IK 7154). Returning to Judaism brings true good in every area of life (IK 6640). Even someone who has left a yeshiva environment can always reconnect (IK 2741), and whoever has left Torah study should return quickly, so the harm stays minimal (IK 2929).
The standing of a baal teshuvah. Every Jew, including one returning after past failings, can attain the deepest attachment to G-d described in Tanya (IK 162). The service of a baal teshuvah has its own unique quality, distinct from that of a tzaddik (IK 5871, 8914), and every Jew should combine both — new beginnings like a tzaddik and correction like a baal teshuvah (IK 9670). Don't pay attention to negative reports about someone's past when his present conduct follows the Torah (IK 4200).
Mockery and family opposition. Don't be deterred or embarrassed by mockers; those who mock often act out of inner conflict. Focus on positive action and join a supportive community (IK 6110, 6550, 6640). When family members object to a Torah life, stay steadfast while avoiding conflict, and focus on your own growth (IK 7528). Build your home on unwavering Torah values, whatever others say (IK 4721).
Helping someone return. Support those returning to observance actively — with encouragement, learning, personal connection and a place in the community (IK 9395). When a friend has left Torah observance, act with urgency, and seek practical advice from those who know the situation (IK 4519, 141). Persistent encouragement from friends, together with tzedakah, can help inspire a return (IK 7617).
See also: Parenting – When a child drifts from Judaism and observance; Teshuvah – How to do teshuvah.