Knowledge is the basic foundation, above which the walls of devotion have to raise.
The reaction of God is hundred times more intensive but it will be in the same direction of action. If you come forward by one step, He will come forward by hundred steps. The necessity is on the side of the souls and therefore the first step should be from the side of the souls only. If your devotion is conditioned by the limits, His grace is also conditioned by the limits of the justice of the wheel of deeds (Karma Chakra). If your devotion is theoretical, His grace is also theoretical. If your devotion is practical, His grace is also practical. Knowledge is the basic foundation, above which the walls of devotion have to raise. The final roof is service to God. Service is sacrifice of work and fruit of work. Only service which is the form of work can have the practical fruit.
The fruit of work is another form of work and is considered as work itself. You worked for one hour and earned hundred rupees. When you sacrifice these hundred rupees to the work of God, it means you have worked for God for one hour. Knowledge is like your qualifying degree. Devotion (theoretical) is like the interview attended by you and the subsequent appointment order. If you sit in your house with the degree and with the appointment order, salary is not paid. Advaitins claim salary for getting the degree itself. Even that degree is not a proper one. Devotees are like the proper degree holders with the proper appointment order and they cannot also claim the salary by sitting in the house. You have to join the job and do work for the entire month. You will get salary at the end of the month for the work you have done during the month.
Devotees recognize the separate Lord and love Him really but are not concentrating on the service to be done to the present incarnation of their generation. They simply dance and sing about the past human incarnations or energetic forms. For their theoretical devotion, God increases their devotion only without any practical fruit. Of course, they are better than people who simply discuss about God always without expression of love in theory and practice. Therefore, service only can get the fruit.
Srimad Bhagavatam 7.5.23-24
"Prahlada Maharaja said: Hearing and chanting about the transcendental holy name, form, qualities, paraphernalia and pastimes of Lord Vishnu, remembering them, serving the lotus feet of the Lord, offering the Lord respectful worship with sixteen types of paraphernalia, offering prayers to the Lord, becoming His servant, considering the Lord one's best friend, and surrendering everything unto Him (in other words, serving Him with the body, mind and words) -- these nine processes are accepted as pure devotional service. One who has dedicated his life to the service of Krishna through these nine methods should be understood to be the most learned person, for he has acquired complete knowledge." http://prabhupadabooks.com/sb/7/5/23-24?d=1
It should be noted here, that chanting and hearing about the Lord are recognized by all the saintly acaryas as pure devotional service. The fruit of such devotional service is love of God free from the desire for any other result.