這是中文式的英語。
從英語的角度來說，句子完全不完整。
也沒有出處。
因為英語裏壓根沒這個說法。
Come and never leave。
如果妳是要表達Once come,never leave.的中文意思的話。
也可以說是流連忘返吧。
流連忘返
indulge in pleasures without stop ；
enjoy oneself so much as to forget to go home ；
enjoy oneself so much that one doesn't want to come back ；
linger on, forgetting to return；
on the scoop
1. The young man who is enchanted by the night scene does not want to go home.
那個年輕人被這夜景所吸引而流連忘返。
來自《現代漢英綜合大詞典》
2. The West Lake in Hangchow is a magnet for visitors.
杭州西湖使遊客流連忘返。
來自辭典例句
3. He is a nighthawk, always hanging around in the night clubs.
他是個夜遊神，常在夜總會流連忘返。
來自辭典例句
4. Only antiquarians and literary amateurs care to look at the gardens with much interest.
只有考古學家和文學愛好者還會在花園裏流連忘返。
來自辭典例句
5. Ordinary Chinese are also fascinated by Singapore as a tourist spot.
民間訪客流連忘返。
來自互聯網