using static System.Console;

using System.Collections.Generic;

using System.Linq;

​

public class Program {

    public static void Main() {

        var lst = new List<string>{"123", "Teste 123 Teste", "ABC", "ABCDE123", "1 2 3" };

        var filter = lst.Where(s => s.Contains("123") || s.Contains("ABC")).Take(3).ToList();

        foreach (var item in filter) WriteLine(item);

    }

}