The Enlarger, The One whose bounty has no limits. He expands and widens the hearts and our souls and gives us sustenance in His Generosity and Mercy.
Allah is Al-Baasit, The One who amplifies all abundance. He is the one who makes the way wide open. He gives plentifully to whoever He wills and reaches out a helping hand to all mankind. Allah gives provision and mercy as He wishes.
From the root b-s-t which has the following classical Arabic connotations: to expand, enlarge, extend, to grant abundance, to provide amply, to spread, widen, to make spacious, or to extend a hand.
In Arabic qabd means to clench, grasp, or seize whereas bast refers to openness. Think closed hand versus open hand, to withhold and to give. These names are often mentioned together for juxtaposition. This emphasizes how Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ, in His infinite wisdom, is the one who either gives or withhold things to whomever He pleases. We find this combination mentioned in Surah Baqarah verse 245:
Man zal lazee yuqridul laaha qardan hasanan fayudaa ‘ifahoo lahoo ad’aafan kaseerah; wallaahu yaqbidu wa yabsutu wa ilaihi turja’oon
"Who is it that would loan Allah a goodly loan so He may multiply it for him many times over? And it is Allah who withholds and grants abundance, and to Him you will be returned."
To constrast with al-Qabid, al-Basit is a display of Allah's mercy of giving without any measure. When Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ wants to give, it is free and infinite. There is no stopping nor restricting it.
Wa law basatal laahur rizqa li’ibaadihee labaghaw fil ardi wa laakiny yunazzilu biqadarim maa yashaaa’; innahoo bi’ibaadihee Khabeerun Baseer
"And if Allah had extended [excessively] provision for His servants, they would have committed tyranny throughout the earth. But He sends [it] down in an amount which He wills. Indeed He is, of His servants, Acquainted and Seeing." (Qur'an 42:47)
The perfection in meaning is understood through viewing the names in pairs as they occur. This is the consensus among scholars, especially when the Names of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ are opposite in meaning. We should try our best to recite them in a similar manner as to see the full picture. These names include al-Qabid (the constrictor) & al-Basit (the extender), al-Awwal (the very first from eternity) & al-Akhir (the very last for enternity), and az-Zaahir (the perceptible) & al-Baatin (the imperceptible).
In a hadith narration, narrated by Anas ibn Malik: The people said: Messenger of Allah, prices have shot up, so fix prices for us. Thereupon the Messenger of Allah (ﷺ) said: Allah is the one Who fixes prices, withholds, gives lavishly and provides, and I hope that when I meet Allah, none of you will have any claim on me for an injustice regarding blood or property. 
In Sahih Muslim, Abu Musa reported Allah's Messenger (ﷺ) as saying that Allah, the Exalted and Glorious, Stretches out His Hand during the night so that the people may repent for the fault committed from dawn till dusk and He stretches out His Hand during the day so that the people may repent for the fault committed from dusk to dawn. (He would accept repentance) before the sun rises in the west (before the Day of Resurrection). A hadith like this has been narrated on the authority of Shu'ba with the same chain of transmitters. 
We can benefit from knowing al-Qabid and al-Basit. We can use these names in supplication, asking Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ to expand our hearts to be reminded in remembrance of Allah. We can call upon these names for rizq as they are closely related. But remember the natural laws of contraction and expansion. We should not be overtly excited for good provision and not be deeply saddened in times of constraint. Accept both as they come and always be grateful to Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ for what's been given.
"Allah extends provision for whom He wills and restricts [it]. And they rejoice in the worldly life, while the worldly life is not, compared to the Hereafter, except [brief] enjoyment." (Qur'an 13:26)
In the tafsir of Maududi speaking of disbelievers of Makkah, "They judged a man’s worth by his wealth and worldly prosperity and not by his faith and righteous conduct. [...] Allah gives His provision to the people abundantly or sparingly for reasons different from those which they presumed and richness or poverty is no criterion by which to judge the worth of people. The real criterion of judging the worth of people is their beliefs and deeds."