Tirmidhi

Explanation:
1:
That is, there should be no words of doubt, hesitation, or slackness; rather, one should supplicate with full determination, firm resolve, and with one's utmost effort, as if saying: "I need this, grant this to me, I must ask only from You, and I must receive only from You," and so on.

Hadith Commentary:
➊
When supplicating, one should display humility and meekness, and also ask Allah with complete certainty.
When making supplication, one should not say, “O Allah, if You will, then grant me,” but rather say, “O Allah! I seek only from You,” because a human being stands before Allah in the position of a beggar.
Allah, the Owner of both worlds, has no deficiency in His treasures, so one should ask with certainty.
There is no one who can compel Allah.
(2)
In any case, the etiquette of supplication is that it should be made with full concentration, utmost humility and submissiveness, and with perfect certainty of acceptance.
And Allah knows best.

Hadith Commentary:
It is prohibited to make supplication (du'a) conditional upon Allah's will; there are two reasons for this:
➊
Making it conditional upon His will could imply that He can be compelled without His desire, whereas this concept is incorrect regarding Allah, because Allah does whatever He wills; no one can compel Him.
➋
Supplicating in this manner suggests indifference towards the request and the One being asked. Therefore, instead of making supplication conditional upon Allah's will, one should supplicate with full determination.
The firmness in the request means that there should be intensity in the asking, no expression of flexibility, and the request should not be made conditional upon His will.
(Sharh Kitab al-Tawhid by al-Ghunayman: 2/291)

1483. Commentary: In this manner, it is as if the supplicant is not truly eager in his supplication, and it appears as though he has no real need. What should be done is that one should ask with firmness and resolve: “O Allah! Grant me this thing,” because when Allah wills to give, no one can prevent Him.

Benefits and Issues:

➊
One should ask for one’s need from Allah Ta’ala while hoping for acceptance.

➋
To say, “If You will,” is not befitting for Allah, therefore it is disliked, because He alone is the One Who gives everything. One should ask Him with the conviction that if He does not accept my supplication, then I have no other door besides His; where else can I go after leaving His door? In any case, such words are disliked in which, instead of certainty, there is an expression of despair.

➌
It is correct to supplicate: “If such-and-such thing is better for me, then grant it to me; otherwise, grant me that which is better for me.” This is exactly the supplication made in the prayer of istikhara.

Takhrij al-Hadith:
[وأخرجه البخاري 6339، من حديث مالك به]
Explanation (Tafaqquh):
➊ Supplication (du'a) should be made to Allah alone.
➋ One should supplicate to Allah with the conviction and certainty that He, out of His grace and bounty, will surely accept the supplication.