Greetings!
According to Bro. Eli in this particular teaching, he advised us not to promise anything as a surprise is even better than a promise fulfilled by force.
Bro. Eli told us not to promise, but to do things silently as this would help us not to be a debtor.
Ecclesiastes 5:4-5 When thou vowest a vow unto God, defer not to pay it; for he hath no pleasure in fools: pay that which thou hast vowed.
Better is it that thou shouldest not vow, than that thou shouldest vow and not pay.
In this scripture above we were made to know that it's good not to vow than to vow and not fulfill it. Vowing and fulfilling can only make us become a debtor and nothing else and this is what God Almighty hates most.
One thing about making promises is that, it raises those that have been promised expectations.
Proverbs 13:12 Hope deferred maketh the heart sick: but when the desire cometh, it is a tree of life.
Also, in the above scripture, we were made to understand that promises raises hope of those being promised which if not fulfilled will make their heart sick, and it is in its fulfillment that they are made to be happy.
So, in conclusion, Bro. Eli advised us not to promise anyone so as not to raise their hope, but instead, surprise them by our secret gift as no one knows what would happen tomorrow according to;
Proverbs 27:1 Boast not thyself of to morrow; for thou knowest not what a day may bring forth.
Thanks for reading.