According to Osho, your reluctance springs from fear and possessiveness masquerading as love. Love and fear cannot coexist; true love is trust, reverence, and freedom. If you truly love, you will bless his search—including Sufi meditation—seeing the Divine in him, not guarding him. Drop surveillance and insecurity; let love flower, and both of you move closer to the Divine.
Trust him and his Sufi meditation; real love lets go of control and fear so you both can grow.